diff --git a/src/Symfony/Component/HttpFoundation/Request.php b/src/Symfony/Component/HttpFoundation/Request.php
index cf6ebbc0b0903..98e2efef45292 100644
--- a/src/Symfony/Component/HttpFoundation/Request.php
+++ b/src/Symfony/Component/HttpFoundation/Request.php
@@ -1564,7 +1564,7 @@ public function getContent($asResource = false)
      */
     public function getETags()
     {
-        return preg_split('/\s*,\s*/', $this->headers->get('if_none_match', ''), -1, \PREG_SPLIT_NO_EMPTY);
+        return preg_split('/\s*,\s*/', $this->headers->get('If-None-Match', ''), -1, \PREG_SPLIT_NO_EMPTY);
     }
 
     /**
diff --git a/src/Symfony/Component/HttpFoundation/Response.php b/src/Symfony/Component/HttpFoundation/Response.php
index 4ab97aaf90538..3c0950f3384cf 100644
--- a/src/Symfony/Component/HttpFoundation/Response.php
+++ b/src/Symfony/Component/HttpFoundation/Response.php
@@ -1079,12 +1079,27 @@ public function isNotModified(Request $request): bool
         $lastModified = $this->headers->get('Last-Modified');
         $modifiedSince = $request->headers->get('If-Modified-Since');
 
-        if ($etags = $request->getETags()) {
-            $notModified = \in_array($this->getEtag(), $etags) || \in_array('*', $etags);
-        }
+        if ($ifNoneMatchEtags = $request->getETags()) {
+            $etag = $this->getEtag();
+            if (0 == strncmp($etag, 'W/', 2)) {
+                $etag = substr($etag, 2);
+            }
+
+            // Use weak comparison as per https://tools.ietf.org/html/rfc7232#section-3.2.
+            foreach ($ifNoneMatchEtags as $ifNoneMatchEtag) {
+                if (0 == strncmp($ifNoneMatchEtag, 'W/', 2)) {
+                    $ifNoneMatchEtag = substr($ifNoneMatchEtag, 2);
+                }
 
-        if ($modifiedSince && $lastModified) {
-            $notModified = strtotime($modifiedSince) >= strtotime($lastModified) && (!$etags || $notModified);
+                if ($ifNoneMatchEtag === $etag || '*' === $ifNoneMatchEtag) {
+                    $notModified = true;
+                    break;
+                }
+            }
+        }
+        // Only do If-Modified-Since date comparison when If-None-Match is not present as per https://tools.ietf.org/html/rfc7232#section-3.3.
+        elseif ($modifiedSince && $lastModified) {
+            $notModified = strtotime($modifiedSince) >= strtotime($lastModified);
         }
 
         if ($notModified) {
diff --git a/src/Symfony/Component/HttpFoundation/Tests/ResponseTest.php b/src/Symfony/Component/HttpFoundation/Tests/ResponseTest.php
index f26302eef1120..b6d714ae5973d 100644
--- a/src/Symfony/Component/HttpFoundation/Tests/ResponseTest.php
+++ b/src/Symfony/Component/HttpFoundation/Tests/ResponseTest.php
@@ -194,7 +194,7 @@ public function testIsNotModifiedEtag()
         $etagTwo = 'randomly_generated_etag_2';
 
         $request = new Request();
-        $request->headers->set('if_none_match', sprintf('%s, %s, %s', $etagOne, $etagTwo, 'etagThree'));
+        $request->headers->set('If-None-Match', sprintf('%s, %s, %s', $etagOne, $etagTwo, 'etagThree'));
 
         $response = new Response();
 
@@ -206,6 +206,38 @@ public function testIsNotModifiedEtag()
 
         $response->headers->set('ETag', '');
         $this->assertFalse($response->isNotModified($request));
+
+        // Test wildcard
+        $request = new Request();
+        $request->headers->set('If-None-Match', '*');
+
+        $response->headers->set('ETag', $etagOne);
+        $this->assertTrue($response->isNotModified($request));
+    }
+
+    public function testIsNotModifiedWeakEtag()
+    {
+        $etag = 'randomly_generated_etag';
+        $weakEtag = 'W/randomly_generated_etag';
+
+        $request = new Request();
+        $request->headers->set('If-None-Match', $etag);
+        $response = new Response();
+
+        $response->headers->set('ETag', $etag);
+        $this->assertTrue($response->isNotModified($request));
+
+        $response->headers->set('ETag', $weakEtag);
+        $this->assertTrue($response->isNotModified($request));
+
+        $request->headers->set('If-None-Match', $weakEtag);
+        $response = new Response();
+
+        $response->headers->set('ETag', $etag);
+        $this->assertTrue($response->isNotModified($request));
+
+        $response->headers->set('ETag', $weakEtag);
+        $this->assertTrue($response->isNotModified($request));
     }
 
     public function testIsNotModifiedLastModifiedAndEtag()
@@ -216,14 +248,14 @@ public function testIsNotModifiedLastModifiedAndEtag()
         $etag = 'randomly_generated_etag';
 
         $request = new Request();
-        $request->headers->set('if_none_match', sprintf('%s, %s', $etag, 'etagThree'));
+        $request->headers->set('If-None-Match', sprintf('%s, %s', $etag, 'etagThree'));
         $request->headers->set('If-Modified-Since', $modified);
 
         $response = new Response();
 
         $response->headers->set('ETag', $etag);
         $response->headers->set('Last-Modified', $after);
-        $this->assertFalse($response->isNotModified($request));
+        $this->assertTrue($response->isNotModified($request));
 
         $response->headers->set('ETag', 'non-existent-etag');
         $response->headers->set('Last-Modified', $before);
@@ -240,7 +272,7 @@ public function testIsNotModifiedIfModifiedSinceAndEtagWithoutLastModified()
         $etag = 'randomly_generated_etag';
 
         $request = new Request();
-        $request->headers->set('if_none_match', sprintf('%s, %s', $etag, 'etagThree'));
+        $request->headers->set('If-None-Match', sprintf('%s, %s', $etag, 'etagThree'));
         $request->headers->set('If-Modified-Since', $modified);
 
         $response = new Response();
diff --git a/src/Symfony/Component/HttpKernel/HttpCache/HttpCache.php b/src/Symfony/Component/HttpKernel/HttpCache/HttpCache.php
index 6c4715802efda..be7042279483a 100644
--- a/src/Symfony/Component/HttpKernel/HttpCache/HttpCache.php
+++ b/src/Symfony/Component/HttpKernel/HttpCache/HttpCache.php
@@ -1,5 +1,14 @@
 <?php
 
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
 /*
  * This file is part of the Symfony package.
  *
@@ -382,7 +391,7 @@ protected function validate(Request $request, Response $entry, $catch = false)
 
         // add our cached last-modified validator
         if ($entry->headers->has('Last-Modified')) {
-            $subRequest->headers->set('if_modified_since', $entry->headers->get('Last-Modified'));
+            $subRequest->headers->set('If-Modified-Since', $entry->headers->get('Last-Modified'));
         }
 
         // Add our cached etag validator to the environment.
@@ -391,7 +400,7 @@ protected function validate(Request $request, Response $entry, $catch = false)
         $cachedEtags = $entry->getEtag() ? [$entry->getEtag()] : [];
         $requestEtags = $request->getETags();
         if ($etags = array_unique(array_merge($cachedEtags, $requestEtags))) {
-            $subRequest->headers->set('if_none_match', implode(', ', $etags));
+            $subRequest->headers->set('If-None-Match', implode(', ', $etags));
         }
 
         $response = $this->forward($subRequest, $catch, $entry);
@@ -444,8 +453,8 @@ protected function fetch(Request $request, $catch = false)
         }
 
         // avoid that the backend sends no content
-        $subRequest->headers->remove('if_modified_since');
-        $subRequest->headers->remove('if_none_match');
+        $subRequest->headers->remove('If-Modified-Since');
+        $subRequest->headers->remove('If-None-Match');
 
         $response = $this->forward($subRequest, $catch);
 
diff --git a/src/Symfony/Component/HttpKernel/Tests/HttpCache/HttpCacheTest.php b/src/Symfony/Component/HttpKernel/Tests/HttpCache/HttpCacheTest.php
index 9bec2f7c94eb1..fc363862ea680 100644
--- a/src/Symfony/Component/HttpKernel/Tests/HttpCache/HttpCacheTest.php
+++ b/src/Symfony/Component/HttpKernel/Tests/HttpCache/HttpCacheTest.php
@@ -156,7 +156,7 @@ public function testRespondsWith304WhenIfNoneMatchMatchesETag()
         $this->assertTraceContains('store');
     }
 
-    public function testRespondsWith304OnlyIfIfNoneMatchAndIfModifiedSinceBothMatch()
+    public function testRespondsWith304WhenIfNoneMatchAndIfModifiedSinceBothMatch()
     {
         $time = \DateTime::createFromFormat('U', time());
 
@@ -172,7 +172,7 @@ public function testRespondsWith304OnlyIfIfNoneMatchAndIfModifiedSinceBothMatch(
         $t = \DateTime::createFromFormat('U', time() - 3600);
         $this->request('GET', '/', ['HTTP_IF_NONE_MATCH' => '12345', 'HTTP_IF_MODIFIED_SINCE' => $t->format(\DATE_RFC2822)]);
         $this->assertHttpKernelIsCalled();
-        $this->assertEquals(200, $this->response->getStatusCode());
+        $this->assertEquals(304, $this->response->getStatusCode());
 
         // only Last-Modified matches
         $this->request('GET', '/', ['HTTP_IF_NONE_MATCH' => '1234', 'HTTP_IF_MODIFIED_SINCE' => $time->format(\DATE_RFC2822)]);
diff --git a/src/Symfony/Component/HttpKernel/composer.json b/src/Symfony/Component/HttpKernel/composer.json
index a2fa2a0ecac5d..74ce9aadb05db 100644
--- a/src/Symfony/Component/HttpKernel/composer.json
+++ b/src/Symfony/Component/HttpKernel/composer.json
@@ -20,7 +20,7 @@
         "symfony/error-handler": "^4.4",
         "symfony/event-dispatcher": "^4.4",
         "symfony/http-client-contracts": "^1.1|^2",
-        "symfony/http-foundation": "^4.4|^5.0",
+        "symfony/http-foundation": "^4.4.24|^5.2.9",
         "symfony/polyfill-ctype": "^1.8",
         "symfony/polyfill-php73": "^1.9",
         "symfony/polyfill-php80": "^1.15",