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GHSA-m7v2-7gxm-vc2v
No affected components available
Description
Symfony\Bridge\Monolog\Command\ServerLogCommand (the server:log console command) is a development-time helper that opens a TCP listener and displays log records pushed to it by the application's logging pipeline. Two unsafe defaults combine into a remotely reachable PHP object-deserialization sink:
- The listener binds to
0.0.0.0:9911by default; it accepts connections on every interface, not only loopback. - Each received frame is processed as
unserialize(base64_decode($message))without anallowed_classesallowlist, without authentication, and without any integrity check. The decoded value is then passed todisplayLog(..., array $record)which assumes (without validating) that the result is an array.
Any host that can reach TCP port 9911 on a machine running server:log can therefore submit attacker-chosen serialized PHP payloads. The minimum impact is an unauthenticated denial of service (sending a non-array, e.g. serialize(new stdClass()), crashes the listener with a type error). Object injection with magic-method side effects (__wakeup() / __destruct() / etc.) is reachable before the array type-check fires; full remote code execution is environment-dependent and contingent on usable gadget chains in the autoload set of the target process.
Resolution
The server:log command no longer binds to all interfaces by default: the default --host is now 127.0.0.1:9911, requiring explicit opt-in to accept off-host traffic. Message decoding is gated by an unserialize() allowlist restricted to the Symfony\Component\VarDumper\Caster\* and Symfony\Component\VarDumper\Cloner\* classes that legitimately appear inside dumped log records; any other class is rejected and the record discarded.
The patch for this issue is available here for branch 5.4.
Credits
Symfony would like to thank Toàn Thắng and Sam Sanoop for reporting the issue and Nicolas Grekas for fixing it.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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