diff --git a/acme/acme_test.go b/acme/acme_test.go
index 3f6e2748f3..a0906708c9 100644
--- a/acme/acme_test.go
+++ b/acme/acme_test.go
@@ -757,7 +757,7 @@ func TestTLSALPN01ChallengeCert(t *testing.T) {
 }
 
 func TestTLSChallengeCertOpt(t *testing.T) {
-	key, err := rsa.GenerateKey(rand.Reader, 512)
+	key, err := rsa.GenerateKey(rand.Reader, 1024)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/acme/autocert/autocert.go b/acme/autocert/autocert.go
index 6b4cdf406d..ccd5b7e3a1 100644
--- a/acme/autocert/autocert.go
+++ b/acme/autocert/autocert.go
@@ -292,6 +292,10 @@ func (m *Manager) GetCertificate(hello *tls.ClientHelloInfo) (*tls.Certificate,
 	}
 
 	// regular domain
+	if err := m.hostPolicy()(ctx, name); err != nil {
+		return nil, err
+	}
+
 	ck := certKey{
 		domain: strings.TrimSuffix(name, "."), // golang.org/issue/18114
 		isRSA:  !supportsECDSA(hello),
@@ -305,9 +309,6 @@ func (m *Manager) GetCertificate(hello *tls.ClientHelloInfo) (*tls.Certificate,
 	}
 
 	// first-time
-	if err := m.hostPolicy()(ctx, name); err != nil {
-		return nil, err
-	}
 	cert, err = m.createCert(ctx, ck)
 	if err != nil {
 		return nil, err
diff --git a/acme/autocert/autocert_test.go b/acme/autocert/autocert_test.go
index 725677574b..269bc2a6c2 100644
--- a/acme/autocert/autocert_test.go
+++ b/acme/autocert/autocert_test.go
@@ -619,7 +619,7 @@ func TestCache(t *testing.T) {
 		PrivateKey:  ecdsaKey,
 	}
 
-	rsaKey, err := rsa.GenerateKey(rand.Reader, 512)
+	rsaKey, err := rsa.GenerateKey(rand.Reader, 1024)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -694,7 +694,7 @@ func TestValidCert(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	key3, err := rsa.GenerateKey(rand.Reader, 512)
+	key3, err := rsa.GenerateKey(rand.Reader, 1024)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/argon2/_asm/go.mod b/argon2/_asm/go.mod
index 41a536dd77..aa51840a9b 100644
--- a/argon2/_asm/go.mod
+++ b/argon2/_asm/go.mod
@@ -4,12 +4,12 @@ go 1.23
 
 require (
 	github.com/mmcloughlin/avo v0.6.0
-	golang.org/x/crypto v0.26.0
+	golang.org/x/crypto v0.33.0
 )
 
 require (
 	golang.org/x/mod v0.20.0 // indirect
 	golang.org/x/sync v0.8.0 // indirect
-	golang.org/x/sys v0.24.0 // indirect
+	golang.org/x/sys v0.30.0 // indirect
 	golang.org/x/tools v0.24.0 // indirect
 )
diff --git a/argon2/_asm/go.sum b/argon2/_asm/go.sum
index 62ea9dfb70..39dd154050 100644
--- a/argon2/_asm/go.sum
+++ b/argon2/_asm/go.sum
@@ -1,12 +1,12 @@
 github.com/mmcloughlin/avo v0.6.0 h1:QH6FU8SKoTLaVs80GA8TJuLNkUYl4VokHKlPhVDg4YY=
 github.com/mmcloughlin/avo v0.6.0/go.mod h1:8CoAGaCSYXtCPR+8y18Y9aB/kxb8JSS6FRI7mSkvD+8=
-golang.org/x/crypto v0.26.0 h1:RrRspgV4mU+YwB4FYnuBoKsUapNIL5cohGAmSH3azsw=
-golang.org/x/crypto v0.26.0/go.mod h1:GY7jblb9wI+FOo5y8/S2oY4zWP07AkOJ4+jxCqdqn54=
+golang.org/x/crypto v0.33.0 h1:IOBPskki6Lysi0lo9qQvbxiQ+FvsCC/YWOecCHAixus=
+golang.org/x/crypto v0.33.0/go.mod h1:bVdXmD7IV/4GdElGPozy6U7lWdRXA4qyRVGJV57uQ5M=
 golang.org/x/mod v0.20.0 h1:utOm6MM3R3dnawAiJgn0y+xvuYRsm1RKM/4giyfDgV0=
 golang.org/x/mod v0.20.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
 golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
-golang.org/x/sys v0.24.0 h1:Twjiwq9dn6R1fQcyiK+wQyHWfaz/BJB+YIpzU/Cv3Xg=
-golang.org/x/sys v0.24.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/tools v0.24.0 h1:J1shsA93PJUEVaUSaay7UXAyE8aimq3GW0pjlolpa24=
 golang.org/x/tools v0.24.0/go.mod h1:YhNqVBIfWHdzvTLs0d8LCuMhkKUgSUKldakyV7W/WDQ=
diff --git a/blake2b/_asm/AVX2/go.mod b/blake2b/_asm/AVX2/go.mod
index c49f1b11ae..78f9070a41 100644
--- a/blake2b/_asm/AVX2/go.mod
+++ b/blake2b/_asm/AVX2/go.mod
@@ -4,13 +4,13 @@ go 1.23
 
 require (
 	github.com/mmcloughlin/avo v0.6.0
-	golang.org/x/crypto v0.26.0
+	golang.org/x/crypto v0.33.0
 
 )
 
 require (
 	golang.org/x/mod v0.20.0 // indirect
 	golang.org/x/sync v0.8.0 // indirect
-	golang.org/x/sys v0.24.0 // indirect
+	golang.org/x/sys v0.30.0 // indirect
 	golang.org/x/tools v0.24.0 // indirect
 )
diff --git a/blake2b/_asm/AVX2/go.sum b/blake2b/_asm/AVX2/go.sum
index 62ea9dfb70..39dd154050 100644
--- a/blake2b/_asm/AVX2/go.sum
+++ b/blake2b/_asm/AVX2/go.sum
@@ -1,12 +1,12 @@
 github.com/mmcloughlin/avo v0.6.0 h1:QH6FU8SKoTLaVs80GA8TJuLNkUYl4VokHKlPhVDg4YY=
 github.com/mmcloughlin/avo v0.6.0/go.mod h1:8CoAGaCSYXtCPR+8y18Y9aB/kxb8JSS6FRI7mSkvD+8=
-golang.org/x/crypto v0.26.0 h1:RrRspgV4mU+YwB4FYnuBoKsUapNIL5cohGAmSH3azsw=
-golang.org/x/crypto v0.26.0/go.mod h1:GY7jblb9wI+FOo5y8/S2oY4zWP07AkOJ4+jxCqdqn54=
+golang.org/x/crypto v0.33.0 h1:IOBPskki6Lysi0lo9qQvbxiQ+FvsCC/YWOecCHAixus=
+golang.org/x/crypto v0.33.0/go.mod h1:bVdXmD7IV/4GdElGPozy6U7lWdRXA4qyRVGJV57uQ5M=
 golang.org/x/mod v0.20.0 h1:utOm6MM3R3dnawAiJgn0y+xvuYRsm1RKM/4giyfDgV0=
 golang.org/x/mod v0.20.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
 golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
-golang.org/x/sys v0.24.0 h1:Twjiwq9dn6R1fQcyiK+wQyHWfaz/BJB+YIpzU/Cv3Xg=
-golang.org/x/sys v0.24.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/tools v0.24.0 h1:J1shsA93PJUEVaUSaay7UXAyE8aimq3GW0pjlolpa24=
 golang.org/x/tools v0.24.0/go.mod h1:YhNqVBIfWHdzvTLs0d8LCuMhkKUgSUKldakyV7W/WDQ=
diff --git a/blake2b/_asm/standard/go.mod b/blake2b/_asm/standard/go.mod
index 8063f1b9c3..a0c60b9e24 100644
--- a/blake2b/_asm/standard/go.mod
+++ b/blake2b/_asm/standard/go.mod
@@ -4,12 +4,12 @@ go 1.23
 
 require (
 	github.com/mmcloughlin/avo v0.6.0
-	golang.org/x/crypto v0.26.0
+	golang.org/x/crypto v0.33.0
 )
 
 require (
 	golang.org/x/mod v0.20.0 // indirect
 	golang.org/x/sync v0.8.0 // indirect
-	golang.org/x/sys v0.24.0 // indirect
+	golang.org/x/sys v0.30.0 // indirect
 	golang.org/x/tools v0.24.0 // indirect
 )
diff --git a/blake2b/_asm/standard/go.sum b/blake2b/_asm/standard/go.sum
index 62ea9dfb70..39dd154050 100644
--- a/blake2b/_asm/standard/go.sum
+++ b/blake2b/_asm/standard/go.sum
@@ -1,12 +1,12 @@
 github.com/mmcloughlin/avo v0.6.0 h1:QH6FU8SKoTLaVs80GA8TJuLNkUYl4VokHKlPhVDg4YY=
 github.com/mmcloughlin/avo v0.6.0/go.mod h1:8CoAGaCSYXtCPR+8y18Y9aB/kxb8JSS6FRI7mSkvD+8=
-golang.org/x/crypto v0.26.0 h1:RrRspgV4mU+YwB4FYnuBoKsUapNIL5cohGAmSH3azsw=
-golang.org/x/crypto v0.26.0/go.mod h1:GY7jblb9wI+FOo5y8/S2oY4zWP07AkOJ4+jxCqdqn54=
+golang.org/x/crypto v0.33.0 h1:IOBPskki6Lysi0lo9qQvbxiQ+FvsCC/YWOecCHAixus=
+golang.org/x/crypto v0.33.0/go.mod h1:bVdXmD7IV/4GdElGPozy6U7lWdRXA4qyRVGJV57uQ5M=
 golang.org/x/mod v0.20.0 h1:utOm6MM3R3dnawAiJgn0y+xvuYRsm1RKM/4giyfDgV0=
 golang.org/x/mod v0.20.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
 golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
-golang.org/x/sys v0.24.0 h1:Twjiwq9dn6R1fQcyiK+wQyHWfaz/BJB+YIpzU/Cv3Xg=
-golang.org/x/sys v0.24.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/tools v0.24.0 h1:J1shsA93PJUEVaUSaay7UXAyE8aimq3GW0pjlolpa24=
 golang.org/x/tools v0.24.0/go.mod h1:YhNqVBIfWHdzvTLs0d8LCuMhkKUgSUKldakyV7W/WDQ=
diff --git a/blake2s/_asm/go.mod b/blake2s/_asm/go.mod
index 9bb23e0eb1..2f6ffc2c6d 100644
--- a/blake2s/_asm/go.mod
+++ b/blake2s/_asm/go.mod
@@ -4,12 +4,12 @@ go 1.23
 
 require (
 	github.com/mmcloughlin/avo v0.6.0
-	golang.org/x/crypto v0.26.0
+	golang.org/x/crypto v0.33.0
 )
 
 require (
 	golang.org/x/mod v0.20.0 // indirect
 	golang.org/x/sync v0.8.0 // indirect
-	golang.org/x/sys v0.24.0 // indirect
+	golang.org/x/sys v0.30.0 // indirect
 	golang.org/x/tools v0.24.0 // indirect
 )
diff --git a/blake2s/_asm/go.sum b/blake2s/_asm/go.sum
index 62ea9dfb70..39dd154050 100644
--- a/blake2s/_asm/go.sum
+++ b/blake2s/_asm/go.sum
@@ -1,12 +1,12 @@
 github.com/mmcloughlin/avo v0.6.0 h1:QH6FU8SKoTLaVs80GA8TJuLNkUYl4VokHKlPhVDg4YY=
 github.com/mmcloughlin/avo v0.6.0/go.mod h1:8CoAGaCSYXtCPR+8y18Y9aB/kxb8JSS6FRI7mSkvD+8=
-golang.org/x/crypto v0.26.0 h1:RrRspgV4mU+YwB4FYnuBoKsUapNIL5cohGAmSH3azsw=
-golang.org/x/crypto v0.26.0/go.mod h1:GY7jblb9wI+FOo5y8/S2oY4zWP07AkOJ4+jxCqdqn54=
+golang.org/x/crypto v0.33.0 h1:IOBPskki6Lysi0lo9qQvbxiQ+FvsCC/YWOecCHAixus=
+golang.org/x/crypto v0.33.0/go.mod h1:bVdXmD7IV/4GdElGPozy6U7lWdRXA4qyRVGJV57uQ5M=
 golang.org/x/mod v0.20.0 h1:utOm6MM3R3dnawAiJgn0y+xvuYRsm1RKM/4giyfDgV0=
 golang.org/x/mod v0.20.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
 golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
-golang.org/x/sys v0.24.0 h1:Twjiwq9dn6R1fQcyiK+wQyHWfaz/BJB+YIpzU/Cv3Xg=
-golang.org/x/sys v0.24.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/tools v0.24.0 h1:J1shsA93PJUEVaUSaay7UXAyE8aimq3GW0pjlolpa24=
 golang.org/x/tools v0.24.0/go.mod h1:YhNqVBIfWHdzvTLs0d8LCuMhkKUgSUKldakyV7W/WDQ=
diff --git a/chacha20poly1305/_asm/go.mod b/chacha20poly1305/_asm/go.mod
index 957baf2a64..23b7bc2c1a 100644
--- a/chacha20poly1305/_asm/go.mod
+++ b/chacha20poly1305/_asm/go.mod
@@ -4,12 +4,12 @@ go 1.23
 
 require (
 	github.com/mmcloughlin/avo v0.6.0
-	golang.org/x/crypto v0.26.0
+	golang.org/x/crypto v0.33.0
 )
 
 require (
 	golang.org/x/mod v0.20.0 // indirect
 	golang.org/x/sync v0.8.0 // indirect
-	golang.org/x/sys v0.24.0 // indirect
+	golang.org/x/sys v0.30.0 // indirect
 	golang.org/x/tools v0.24.0 // indirect
 )
diff --git a/chacha20poly1305/_asm/go.sum b/chacha20poly1305/_asm/go.sum
index 62ea9dfb70..39dd154050 100644
--- a/chacha20poly1305/_asm/go.sum
+++ b/chacha20poly1305/_asm/go.sum
@@ -1,12 +1,12 @@
 github.com/mmcloughlin/avo v0.6.0 h1:QH6FU8SKoTLaVs80GA8TJuLNkUYl4VokHKlPhVDg4YY=
 github.com/mmcloughlin/avo v0.6.0/go.mod h1:8CoAGaCSYXtCPR+8y18Y9aB/kxb8JSS6FRI7mSkvD+8=
-golang.org/x/crypto v0.26.0 h1:RrRspgV4mU+YwB4FYnuBoKsUapNIL5cohGAmSH3azsw=
-golang.org/x/crypto v0.26.0/go.mod h1:GY7jblb9wI+FOo5y8/S2oY4zWP07AkOJ4+jxCqdqn54=
+golang.org/x/crypto v0.33.0 h1:IOBPskki6Lysi0lo9qQvbxiQ+FvsCC/YWOecCHAixus=
+golang.org/x/crypto v0.33.0/go.mod h1:bVdXmD7IV/4GdElGPozy6U7lWdRXA4qyRVGJV57uQ5M=
 golang.org/x/mod v0.20.0 h1:utOm6MM3R3dnawAiJgn0y+xvuYRsm1RKM/4giyfDgV0=
 golang.org/x/mod v0.20.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
 golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
-golang.org/x/sys v0.24.0 h1:Twjiwq9dn6R1fQcyiK+wQyHWfaz/BJB+YIpzU/Cv3Xg=
-golang.org/x/sys v0.24.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/tools v0.24.0 h1:J1shsA93PJUEVaUSaay7UXAyE8aimq3GW0pjlolpa24=
 golang.org/x/tools v0.24.0/go.mod h1:YhNqVBIfWHdzvTLs0d8LCuMhkKUgSUKldakyV7W/WDQ=
diff --git a/go.mod b/go.mod
index b08fd5cd3a..a0f577ac3b 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module golang.org/x/crypto
 
-go 1.20
+go 1.23.0
 
 require (
 	golang.org/x/net v0.21.0 // tagx:ignore
diff --git a/internal/poly1305/_asm/go.mod b/internal/poly1305/_asm/go.mod
index 47f2b758ef..cabd9519b2 100644
--- a/internal/poly1305/_asm/go.mod
+++ b/internal/poly1305/_asm/go.mod
@@ -4,12 +4,12 @@ go 1.23
 
 require (
 	github.com/mmcloughlin/avo v0.6.0
-	golang.org/x/crypto v0.26.0
+	golang.org/x/crypto v0.33.0
 )
 
 require (
 	golang.org/x/mod v0.20.0 // indirect
 	golang.org/x/sync v0.8.0 // indirect
-	golang.org/x/sys v0.24.0 // indirect
+	golang.org/x/sys v0.30.0 // indirect
 	golang.org/x/tools v0.24.0 // indirect
 )
diff --git a/internal/poly1305/_asm/go.sum b/internal/poly1305/_asm/go.sum
index 62ea9dfb70..39dd154050 100644
--- a/internal/poly1305/_asm/go.sum
+++ b/internal/poly1305/_asm/go.sum
@@ -1,12 +1,12 @@
 github.com/mmcloughlin/avo v0.6.0 h1:QH6FU8SKoTLaVs80GA8TJuLNkUYl4VokHKlPhVDg4YY=
 github.com/mmcloughlin/avo v0.6.0/go.mod h1:8CoAGaCSYXtCPR+8y18Y9aB/kxb8JSS6FRI7mSkvD+8=
-golang.org/x/crypto v0.26.0 h1:RrRspgV4mU+YwB4FYnuBoKsUapNIL5cohGAmSH3azsw=
-golang.org/x/crypto v0.26.0/go.mod h1:GY7jblb9wI+FOo5y8/S2oY4zWP07AkOJ4+jxCqdqn54=
+golang.org/x/crypto v0.33.0 h1:IOBPskki6Lysi0lo9qQvbxiQ+FvsCC/YWOecCHAixus=
+golang.org/x/crypto v0.33.0/go.mod h1:bVdXmD7IV/4GdElGPozy6U7lWdRXA4qyRVGJV57uQ5M=
 golang.org/x/mod v0.20.0 h1:utOm6MM3R3dnawAiJgn0y+xvuYRsm1RKM/4giyfDgV0=
 golang.org/x/mod v0.20.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
 golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
-golang.org/x/sys v0.24.0 h1:Twjiwq9dn6R1fQcyiK+wQyHWfaz/BJB+YIpzU/Cv3Xg=
-golang.org/x/sys v0.24.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/tools v0.24.0 h1:J1shsA93PJUEVaUSaay7UXAyE8aimq3GW0pjlolpa24=
 golang.org/x/tools v0.24.0/go.mod h1:YhNqVBIfWHdzvTLs0d8LCuMhkKUgSUKldakyV7W/WDQ=
diff --git a/salsa20/salsa/_asm/go.mod b/salsa20/salsa/_asm/go.mod
index 0cf7f76881..2de7bf107b 100644
--- a/salsa20/salsa/_asm/go.mod
+++ b/salsa20/salsa/_asm/go.mod
@@ -4,7 +4,7 @@ go 1.23
 
 require (
 	github.com/mmcloughlin/avo v0.6.0
-	golang.org/x/crypto v0.26.0
+	golang.org/x/crypto v0.33.0
 )
 
 require (
diff --git a/salsa20/salsa/_asm/go.sum b/salsa20/salsa/_asm/go.sum
index e5970800fb..4d48823d47 100644
--- a/salsa20/salsa/_asm/go.sum
+++ b/salsa20/salsa/_asm/go.sum
@@ -1,7 +1,7 @@
 github.com/mmcloughlin/avo v0.6.0 h1:QH6FU8SKoTLaVs80GA8TJuLNkUYl4VokHKlPhVDg4YY=
 github.com/mmcloughlin/avo v0.6.0/go.mod h1:8CoAGaCSYXtCPR+8y18Y9aB/kxb8JSS6FRI7mSkvD+8=
-golang.org/x/crypto v0.26.0 h1:RrRspgV4mU+YwB4FYnuBoKsUapNIL5cohGAmSH3azsw=
-golang.org/x/crypto v0.26.0/go.mod h1:GY7jblb9wI+FOo5y8/S2oY4zWP07AkOJ4+jxCqdqn54=
+golang.org/x/crypto v0.33.0 h1:IOBPskki6Lysi0lo9qQvbxiQ+FvsCC/YWOecCHAixus=
+golang.org/x/crypto v0.33.0/go.mod h1:bVdXmD7IV/4GdElGPozy6U7lWdRXA4qyRVGJV57uQ5M=
 golang.org/x/mod v0.20.0 h1:utOm6MM3R3dnawAiJgn0y+xvuYRsm1RKM/4giyfDgV0=
 golang.org/x/mod v0.20.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
diff --git a/sha3/_asm/go.mod b/sha3/_asm/go.mod
index 265a88d077..cd16c586a9 100644
--- a/sha3/_asm/go.mod
+++ b/sha3/_asm/go.mod
@@ -4,12 +4,12 @@ go 1.22
 
 require (
 	github.com/mmcloughlin/avo v0.6.0
-	golang.org/x/crypto v0.25.0
+	golang.org/x/crypto v0.33.0
 )
 
 require (
 	golang.org/x/mod v0.19.0 // indirect
 	golang.org/x/sync v0.7.0 // indirect
-	golang.org/x/sys v0.22.0 // indirect
+	golang.org/x/sys v0.30.0 // indirect
 	golang.org/x/tools v0.23.0 // indirect
 )
diff --git a/sha3/_asm/go.sum b/sha3/_asm/go.sum
index a2552b8eb9..6083f86740 100644
--- a/sha3/_asm/go.sum
+++ b/sha3/_asm/go.sum
@@ -1,12 +1,12 @@
 github.com/mmcloughlin/avo v0.6.0 h1:QH6FU8SKoTLaVs80GA8TJuLNkUYl4VokHKlPhVDg4YY=
 github.com/mmcloughlin/avo v0.6.0/go.mod h1:8CoAGaCSYXtCPR+8y18Y9aB/kxb8JSS6FRI7mSkvD+8=
-golang.org/x/crypto v0.25.0 h1:ypSNr+bnYL2YhwoMt2zPxHFmbAN1KZs/njMG3hxUp30=
-golang.org/x/crypto v0.25.0/go.mod h1:T+wALwcMOSE0kXgUAnPAHqTLW+XHgcELELW8VaDgm/M=
+golang.org/x/crypto v0.33.0 h1:IOBPskki6Lysi0lo9qQvbxiQ+FvsCC/YWOecCHAixus=
+golang.org/x/crypto v0.33.0/go.mod h1:bVdXmD7IV/4GdElGPozy6U7lWdRXA4qyRVGJV57uQ5M=
 golang.org/x/mod v0.19.0 h1:fEdghXQSo20giMthA7cd28ZC+jts4amQ3YMXiP5oMQ8=
 golang.org/x/mod v0.19.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/sync v0.7.0 h1:YsImfSBoP9QPYL0xyKJPq0gcaJdG3rInoqxTWbfQu9M=
 golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
-golang.org/x/sys v0.22.0 h1:RI27ohtqKCnwULzJLqkv897zojh5/DwS/ENaMzUOaWI=
-golang.org/x/sys v0.22.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/tools v0.23.0 h1:SGsXPZ+2l4JsgaCKkx+FQ9YZ5XEtA1GZYuoDjenLjvg=
 golang.org/x/tools v0.23.0/go.mod h1:pnu6ufv6vQkll6szChhK3C3L/ruaIv5eBeztNG8wtsI=
diff --git a/ssh/certs_test.go b/ssh/certs_test.go
index 66000f19a2..6208bb37a9 100644
--- a/ssh/certs_test.go
+++ b/ssh/certs_test.go
@@ -15,14 +15,12 @@ import (
 	"reflect"
 	"testing"
 	"time"
-)
 
-// Cert generated by ssh-keygen 6.0p1 Debian-4.
-// % ssh-keygen -s ca-key -I test user-key
-const exampleSSHCert = `ssh-rsa-cert-v01@openssh.com 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`
+	"golang.org/x/crypto/ssh/testdata"
+)
 
 func TestParseCert(t *testing.T) {
-	authKeyBytes := []byte(exampleSSHCert)
+	authKeyBytes := bytes.TrimSuffix(testdata.SSHCertificates["rsa"], []byte(" host.example.com\n"))
 
 	key, _, _, rest, err := ParseAuthorizedKey(authKeyBytes)
 	if err != nil {
@@ -103,7 +101,7 @@ func TestParseCertWithOptions(t *testing.T) {
 }
 
 func TestValidateCert(t *testing.T) {
-	key, _, _, _, err := ParseAuthorizedKey([]byte(exampleSSHCert))
+	key, _, _, _, err := ParseAuthorizedKey(testdata.SSHCertificates["rsa-user-testcertificate"])
 	if err != nil {
 		t.Fatalf("ParseAuthorizedKey: %v", err)
 	}
@@ -116,7 +114,7 @@ func TestValidateCert(t *testing.T) {
 		return bytes.Equal(k.Marshal(), validCert.SignatureKey.Marshal())
 	}
 
-	if err := checker.CheckCert("user", validCert); err != nil {
+	if err := checker.CheckCert("testcertificate", validCert); err != nil {
 		t.Errorf("Unable to validate certificate: %v", err)
 	}
 	invalidCert := &Certificate{
@@ -125,7 +123,7 @@ func TestValidateCert(t *testing.T) {
 		ValidBefore:  CertTimeInfinity,
 		Signature:    &Signature{},
 	}
-	if err := checker.CheckCert("user", invalidCert); err == nil {
+	if err := checker.CheckCert("testcertificate", invalidCert); err == nil {
 		t.Error("Invalid cert signature passed validation")
 	}
 }
diff --git a/ssh/handshake.go b/ssh/handshake.go
index fef687db0e..c9202b05da 100644
--- a/ssh/handshake.go
+++ b/ssh/handshake.go
@@ -25,6 +25,11 @@ const debugHandshake = false
 // quickly.
 const chanSize = 16
 
+// maxPendingPackets sets the maximum number of packets to queue while waiting
+// for KEX to complete. This limits the total pending data to maxPendingPackets
+// * maxPacket bytes, which is ~16.8MB.
+const maxPendingPackets = 64
+
 // keyingTransport is a packet based transport that supports key
 // changes. It need not be thread-safe. It should pass through
 // msgNewKeys in both directions.
@@ -73,11 +78,19 @@ type handshakeTransport struct {
 	incoming  chan []byte
 	readError error
 
-	mu               sync.Mutex
-	writeError       error
-	sentInitPacket   []byte
-	sentInitMsg      *kexInitMsg
-	pendingPackets   [][]byte // Used when a key exchange is in progress.
+	mu sync.Mutex
+	// Condition for the above mutex. It is used to notify a completed key
+	// exchange or a write failure. Writes can wait for this condition while a
+	// key exchange is in progress.
+	writeCond      *sync.Cond
+	writeError     error
+	sentInitPacket []byte
+	sentInitMsg    *kexInitMsg
+	// Used to queue writes when a key exchange is in progress. The length is
+	// limited by pendingPacketsSize. Once full, writes will block until the key
+	// exchange is completed or an error occurs. If not empty, it is emptied
+	// all at once when the key exchange is completed in kexLoop.
+	pendingPackets   [][]byte
 	writePacketsLeft uint32
 	writeBytesLeft   int64
 	userAuthComplete bool // whether the user authentication phase is complete
@@ -134,6 +147,7 @@ func newHandshakeTransport(conn keyingTransport, config *Config, clientVersion,
 
 		config: config,
 	}
+	t.writeCond = sync.NewCond(&t.mu)
 	t.resetReadThresholds()
 	t.resetWriteThresholds()
 
@@ -260,6 +274,7 @@ func (t *handshakeTransport) recordWriteError(err error) {
 	defer t.mu.Unlock()
 	if t.writeError == nil && err != nil {
 		t.writeError = err
+		t.writeCond.Broadcast()
 	}
 }
 
@@ -363,6 +378,8 @@ write:
 			}
 		}
 		t.pendingPackets = t.pendingPackets[:0]
+		// Unblock writePacket if waiting for KEX.
+		t.writeCond.Broadcast()
 		t.mu.Unlock()
 	}
 
@@ -577,11 +594,20 @@ func (t *handshakeTransport) writePacket(p []byte) error {
 	}
 
 	if t.sentInitMsg != nil {
-		// Copy the packet so the writer can reuse the buffer.
-		cp := make([]byte, len(p))
-		copy(cp, p)
-		t.pendingPackets = append(t.pendingPackets, cp)
-		return nil
+		if len(t.pendingPackets) < maxPendingPackets {
+			// Copy the packet so the writer can reuse the buffer.
+			cp := make([]byte, len(p))
+			copy(cp, p)
+			t.pendingPackets = append(t.pendingPackets, cp)
+			return nil
+		}
+		for t.sentInitMsg != nil {
+			// Block and wait for KEX to complete or an error.
+			t.writeCond.Wait()
+			if t.writeError != nil {
+				return t.writeError
+			}
+		}
 	}
 
 	if t.writeBytesLeft > 0 {
@@ -598,6 +624,7 @@ func (t *handshakeTransport) writePacket(p []byte) error {
 
 	if err := t.pushPacket(p); err != nil {
 		t.writeError = err
+		t.writeCond.Broadcast()
 	}
 
 	return nil
diff --git a/ssh/handshake_test.go b/ssh/handshake_test.go
index 2bc607b649..019e47fa05 100644
--- a/ssh/handshake_test.go
+++ b/ssh/handshake_test.go
@@ -539,6 +539,226 @@ func TestDisconnect(t *testing.T) {
 	}
 }
 
+type mockKeyingTransport struct {
+	packetConn
+	kexInitAllowed chan struct{}
+	kexInitSent    chan struct{}
+}
+
+func (n *mockKeyingTransport) prepareKeyChange(*algorithms, *kexResult) error {
+	return nil
+}
+
+func (n *mockKeyingTransport) writePacket(packet []byte) error {
+	if packet[0] == msgKexInit {
+		<-n.kexInitAllowed
+		n.kexInitSent <- struct{}{}
+	}
+	return n.packetConn.writePacket(packet)
+}
+
+func (n *mockKeyingTransport) readPacket() ([]byte, error) {
+	return n.packetConn.readPacket()
+}
+
+func (n *mockKeyingTransport) setStrictMode() error { return nil }
+
+func (n *mockKeyingTransport) setInitialKEXDone() {}
+
+func TestHandshakePendingPacketsWait(t *testing.T) {
+	a, b := memPipe()
+
+	trS := &mockKeyingTransport{
+		packetConn:     a,
+		kexInitAllowed: make(chan struct{}, 2),
+		kexInitSent:    make(chan struct{}, 2),
+	}
+	// Allow the first KEX.
+	trS.kexInitAllowed <- struct{}{}
+
+	trC := &mockKeyingTransport{
+		packetConn:     b,
+		kexInitAllowed: make(chan struct{}, 2),
+		kexInitSent:    make(chan struct{}, 2),
+	}
+	// Allow the first KEX.
+	trC.kexInitAllowed <- struct{}{}
+
+	clientConf := &ClientConfig{
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+	clientConf.SetDefaults()
+
+	v := []byte("version")
+	client := newClientTransport(trC, v, v, clientConf, "addr", nil)
+
+	serverConf := &ServerConfig{}
+	serverConf.AddHostKey(testSigners["ecdsa"])
+	serverConf.AddHostKey(testSigners["rsa"])
+	serverConf.SetDefaults()
+	server := newServerTransport(trS, v, v, serverConf)
+
+	if err := server.waitSession(); err != nil {
+		t.Fatalf("server.waitSession: %v", err)
+	}
+	if err := client.waitSession(); err != nil {
+		t.Fatalf("client.waitSession: %v", err)
+	}
+
+	<-trC.kexInitSent
+	<-trS.kexInitSent
+
+	// Allow and request new KEX server side.
+	trS.kexInitAllowed <- struct{}{}
+	server.requestKeyExchange()
+	// Wait until the KEX init is sent.
+	<-trS.kexInitSent
+	// The client is not allowed to respond to the KEX, so writes will be
+	// blocked on the server side once the packets queue is full.
+	for i := 0; i < maxPendingPackets; i++ {
+		p := []byte{msgRequestSuccess, byte(i)}
+		if err := server.writePacket(p); err != nil {
+			t.Errorf("unexpected write error: %v", err)
+		}
+	}
+	// The packets queue is now full, the next write will block.
+	server.mu.Lock()
+	if len(server.pendingPackets) != maxPendingPackets {
+		t.Errorf("unexpected pending packets size; got: %d, want: %d", len(server.pendingPackets), maxPendingPackets)
+	}
+	server.mu.Unlock()
+
+	writeDone := make(chan struct{})
+	go func() {
+		defer close(writeDone)
+
+		p := []byte{msgRequestSuccess, byte(65)}
+		// This write will block until KEX completes.
+		err := server.writePacket(p)
+		if err != nil {
+			t.Errorf("unexpected write error: %v", err)
+		}
+	}()
+
+	// Consume packets on the client side
+	readDone := make(chan bool)
+	go func() {
+		defer close(readDone)
+
+		for {
+			if _, err := client.readPacket(); err != nil {
+				if err != io.EOF {
+					t.Errorf("unexpected read error: %v", err)
+				}
+				break
+			}
+		}
+	}()
+
+	// Allow the client to reply to the KEX and so unblock the write goroutine.
+	trC.kexInitAllowed <- struct{}{}
+	<-trC.kexInitSent
+	<-writeDone
+	// Close the client to unblock the read goroutine.
+	client.Close()
+	<-readDone
+	server.Close()
+}
+
+func TestHandshakePendingPacketsError(t *testing.T) {
+	a, b := memPipe()
+
+	trS := &mockKeyingTransport{
+		packetConn:     a,
+		kexInitAllowed: make(chan struct{}, 2),
+		kexInitSent:    make(chan struct{}, 2),
+	}
+	// Allow the first KEX.
+	trS.kexInitAllowed <- struct{}{}
+
+	trC := &mockKeyingTransport{
+		packetConn:     b,
+		kexInitAllowed: make(chan struct{}, 2),
+		kexInitSent:    make(chan struct{}, 2),
+	}
+	// Allow the first KEX.
+	trC.kexInitAllowed <- struct{}{}
+
+	clientConf := &ClientConfig{
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+	clientConf.SetDefaults()
+
+	v := []byte("version")
+	client := newClientTransport(trC, v, v, clientConf, "addr", nil)
+
+	serverConf := &ServerConfig{}
+	serverConf.AddHostKey(testSigners["ecdsa"])
+	serverConf.AddHostKey(testSigners["rsa"])
+	serverConf.SetDefaults()
+	server := newServerTransport(trS, v, v, serverConf)
+
+	if err := server.waitSession(); err != nil {
+		t.Fatalf("server.waitSession: %v", err)
+	}
+	if err := client.waitSession(); err != nil {
+		t.Fatalf("client.waitSession: %v", err)
+	}
+
+	<-trC.kexInitSent
+	<-trS.kexInitSent
+
+	// Allow and request new KEX server side.
+	trS.kexInitAllowed <- struct{}{}
+	server.requestKeyExchange()
+	// Wait until the KEX init is sent.
+	<-trS.kexInitSent
+	// The client is not allowed to respond to the KEX, so writes will be
+	// blocked on the server side once the packets queue is full.
+	for i := 0; i < maxPendingPackets; i++ {
+		p := []byte{msgRequestSuccess, byte(i)}
+		if err := server.writePacket(p); err != nil {
+			t.Errorf("unexpected write error: %v", err)
+		}
+	}
+	// The packets queue is now full, the next write will block.
+	writeDone := make(chan struct{})
+	go func() {
+		defer close(writeDone)
+
+		p := []byte{msgRequestSuccess, byte(65)}
+		// This write will block until KEX completes.
+		err := server.writePacket(p)
+		if err != io.EOF {
+			t.Errorf("unexpected write error: %v", err)
+		}
+	}()
+
+	// Consume packets on the client side
+	readDone := make(chan bool)
+	go func() {
+		defer close(readDone)
+
+		for {
+			if _, err := client.readPacket(); err != nil {
+				if err != io.EOF {
+					t.Errorf("unexpected read error: %v", err)
+				}
+				break
+			}
+		}
+	}()
+
+	// Close the server to unblock the write after an error
+	server.Close()
+	<-writeDone
+	// Unblock the pending write and close the client to unblock the read
+	// goroutine.
+	trC.kexInitAllowed <- struct{}{}
+	client.Close()
+	<-readDone
+}
+
 func TestHandshakeRekeyDefault(t *testing.T) {
 	clientConf := &ClientConfig{
 		Config: Config{
diff --git a/x509roots/fallback/bundle.go b/x509roots/fallback/bundle.go
index d6653ac69b..89d97ba091 100644
--- a/x509roots/fallback/bundle.go
+++ b/x509roots/fallback/bundle.go
@@ -1,7 +1,5 @@
 // Code generated by gen_fallback_bundle.go; DO NOT EDIT.
 
-//go:build go1.20
-
 package fallback
 
 import "crypto/x509"
diff --git a/x509roots/fallback/fallback.go b/x509roots/fallback/fallback.go
index 31413595fa..42717e1cd4 100644
--- a/x509roots/fallback/fallback.go
+++ b/x509roots/fallback/fallback.go
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.20
-
 // Package fallback embeds a set of fallback X.509 trusted roots in the
 // application by automatically invoking [x509.SetFallbackRoots]. This allows
 // the application to work correctly even if the operating system does not
diff --git a/x509roots/fallback/go.mod b/x509roots/fallback/go.mod
index d8974bf9fe..6ffde44ff8 100644
--- a/x509roots/fallback/go.mod
+++ b/x509roots/fallback/go.mod
@@ -1,3 +1,3 @@
 module golang.org/x/crypto/x509roots/fallback
 
-go 1.20
+go 1.23.0
diff --git a/x509roots/gen_fallback_bundle.go b/x509roots/gen_fallback_bundle.go
index ffea49b1e8..246f60ca9b 100644
--- a/x509roots/gen_fallback_bundle.go
+++ b/x509roots/gen_fallback_bundle.go
@@ -27,8 +27,6 @@ import (
 
 const tmpl = `// Code generated by gen_fallback_bundle.go; DO NOT EDIT.
 
-//go:build go1.20
-
 package fallback
 
 import "crypto/x509"