CVE-2026-47767 — Vulnerability in symfony/symfony — CVE Details

### Description CVE-2024-50340 (GHSA-x8vp-gf4q-mw5j) addressed an issue where, with `register_argc_argv=On`, a crafted query string let an unauthenticated GET change the kernel environment and debug flag by feeding `--env`/`--no-debug` through `$_SERVER['argv']`. The fix shipped in `symfony/runtime` 5.4.46 / 6.4.14 / 7.1.7 gated the argv read on `empty($_GET)` as a proxy for "is this a CLI invocation". That proxy is unsafe: `parse_str()` (which builds `$_GET`) and the web SAPI (which builds `$_SERVER['argv']` from the raw query when `register_argc_argv=On`) do not agree on every input, so an attacker can craft a query that leaves `$_GET` empty while `$_SERVER['argv']` carries the attacker's flags. `SymfonyRuntime::getInput()` then parses them, restoring the exact primitive CVE-2024-50340 was meant to prevent. Preconditions and impact match the original CVE: web SAPI, `register_argc_argv=On`, app booted through `symfony/runtime`; from an unauthenticated GET an attacker can flip `APP_ENV` and toggle `APP_DEBUG`. ### Resolution `SymfonyRuntime` now gates the argv read on `isset($_SERVER['QUERY_STRING'])` rather than on `empty($_GET)`. `QUERY_STRING` is the same input the SAPI uses to build argv, so the security check and the thing it protects no longer parse different sources. Worker SAPIs (FrankenPHP / RoadRunner / Swoole) keep working because the runtime constructor runs once at boot when `QUERY_STRING` is unset. The patch for this issue is available [here](https://github.com/symfony/symfony/commit/3228c3806ee511008bea19a95084d460b17e5d25) for branch 5.4. ### Credits SymfonyRuntime would like to thank 0xEr3n for reporting the issue and Nicolas Grekas for providing the fix.