symfony
diff --git a/‎src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php
+6Lines changed: 6 additions & 0 deletions b/‎src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php
+6Lines changed: 6 additions & 0 deletions
diff --git a/‎src/Symfony/Component/HttpFoundation/Tests/Session/Storage/NativeSessionStorageTest.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/HttpFoundation/Tests/Session/Storage/NativeSessionStorageTest.php
+9Lines changed: 9 additions & 0 deletions b/‎src/Symfony/Component/HttpFoundation/Tests/Session/Storage/NativeSessionStorageTest.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/HttpFoundation/Tests/Session/Storage/NativeSessionStorageTest.php
+9Lines changed: 9 additions & 0 deletions
@@ -152,6 +152,12 @@ public function start()
             throw new \RuntimeException(sprintf('Failed to start the session because headers have already been sent by "%s" at line %d.', $file, $line));
         }
 
+        $sessionId = $_COOKIE[session_name()] ?? null;
+        if ($sessionId && !preg_match('/^[a-zA-Z0-9,-]{22,}$/', $sessionId)) {
+            // the session ID in the header is invalid, create a new one
+            session_id(session_create_id());
+        }
+
         // ok to try and start the session
         if (!session_start()) {
             throw new \RuntimeException('Failed to start the session.');
 
@@ -293,4 +293,13 @@ public function testGetBagsOnceSessionStartedIsIgnored()
 
         $this->assertEquals($storage->getBag('flashes'), $bag);
     }
+
+    public function testRegenerateInvalidSessionId()
+    {
+        $_COOKIE[session_name()] = '&~[';
+        $started = (new NativeSessionStorage())->start();
+
+        $this->assertTrue($started);
+        $this->assertMatchesRegularExpression('/^[a-zA-Z0-9,-]{22,}$/', session_id());
+    }
 }
Original file line number	Diff line number	Diff line change
`@@ -293,4 +293,13 @@ public function testGetBagsOnceSessionStartedIsIgnored()`
`293`	`293`
`294`	`294`	`$this->assertEquals($storage->getBag('flashes'), $bag);`
`295`	`295`	`}`
	`296`	`+`
	`297`	`+ public function testRegenerateInvalidSessionId()`
	`298`	`+ {`
	`299`	`+ $_COOKIE[session_name()] = '&~[';`
	`300`	`+ $started = (new NativeSessionStorage())->start();`
	`301`	`+`
	`302`	`+ $this->assertTrue($started);`
	`303`	`+ $this->assertMatchesRegularExpression('/^[a-zA-Z0-9,-]{22,}$/', session_id());`
	`304`	`+ }`
`296`	`305`	`}`