diff --git a/src/Symfony/Component/HttpFoundation/IpUtils.php b/src/Symfony/Component/HttpFoundation/IpUtils.php
index 9a1afa7bf498a..2f31284e36c69 100644
--- a/src/Symfony/Component/HttpFoundation/IpUtils.php
+++ b/src/Symfony/Component/HttpFoundation/IpUtils.php
@@ -86,7 +86,7 @@ public static function checkIp4(?string $requestIp, string $ip)
             [$address, $netmask] = explode('/', $ip, 2);
 
             if ('0' === $netmask) {
-                return self::$checkedIps[$cacheKey] = filter_var($address, \FILTER_VALIDATE_IP, \FILTER_FLAG_IPV4);
+                return self::$checkedIps[$cacheKey] = false !== filter_var($address, \FILTER_VALIDATE_IP, \FILTER_FLAG_IPV4);
             }
 
             if ($netmask < 0 || $netmask > 32) {
diff --git a/src/Symfony/Component/HttpFoundation/Tests/IpUtilsTest.php b/src/Symfony/Component/HttpFoundation/Tests/IpUtilsTest.php
index d6d3728db1401..33d67303a831d 100644
--- a/src/Symfony/Component/HttpFoundation/Tests/IpUtilsTest.php
+++ b/src/Symfony/Component/HttpFoundation/Tests/IpUtilsTest.php
@@ -164,4 +164,21 @@ public function anonymizedIpData()
             ['::123.234.235.236', '::123.234.235.0'], // deprecated IPv4-compatible IPv6 address
         ];
     }
+
+    /**
+     * @dataProvider getIp4SubnetMaskZeroData
+     */
+    public function testIp4SubnetMaskZero($matches, $remoteAddr, $cidr)
+    {
+        $this->assertSame($matches, IpUtils::checkIp4($remoteAddr, $cidr));
+    }
+
+    public function getIp4SubnetMaskZeroData()
+    {
+        return [
+            [true, '1.2.3.4', '0.0.0.0/0'],
+            [true, '1.2.3.4', '192.168.1.0/0'],
+            [false, '1.2.3.4', '256.256.256/0'], // invalid CIDR notation
+        ];
+    }
 }