Twig Sandbox: __toString() Runs on Objects in Arrays Without a Check

Published as "Unguarded calls to __toString() when nesting an object into an array"

low Symfony Twig · Last reviewed Nov 9, 2026

CVE: CVE-2024-51754
GHSA: GHSA-6377-hfv9-hqf6
Packagist: PKSA-yhcn-xrg3-68b1
Reported: Nov 6, 2024

Lets untrusted templates call __toString() on objects the sandbox policy blocks, when the object sits in an array or an argument list.

Affected and fixed versions

In twig/twig. Find the row for the version you run, and update to the release next to it.

If you run	Update to	Support
3.12.0 – 3.14.0	3.14.1	Supported

Show 3 older branches, no longer supported

1.0.0 – 1.x	3.11.2
2.0.0 – 2.x	3.11.2
3.0.0 – 3.11.1	3.11.2

Upgrade

Run the line for the branch you are on.

composer require twig/twig:^3.14.1

What this means

Twig's sandbox lets you render templates written by people you don't fully trust, under a security policy that limits which methods they can call. Before this fix, a sandboxed template could call __toString() on an object even when the policy didn't allow it, as long as the object was inside an array or passed as an argument to a function or filter.

Who is affected

Apps that render untrusted templates with Twig's SandboxExtension, on twig/twig below 3.11.2, or 3.12.0 and later below 3.14.1. The attacker needs to be able to write templates, and gets whatever the blocked __toString() methods return. Apps that don't use the sandbox are not affected. Twig 1.x and 2.x are no longer maintained and stay vulnerable.

What to do

Update to 3.11.2 on the 3.11 branch, or to 3.14.1. The sandbox now checks __toString() calls on all objects. On Twig 1.x or 2.x, move to 3.x. See Twig's advisory and the fix.

Reported by Jamie Schouten.

Check your app with an agent

Paste this into a coding agent that can read your project, such as Claude Code, Codex or Amp. It checks your composer.lock against the versions above and tells you what to update, without changing anything.

Check whether the PHP project you have access to is affected by this security advisory, and tell me what to update. Do a read-only check: don't edit files, don't run composer update or composer require, and don't try to reproduce the flaw.

Advisory: Twig Sandbox: __toString() Runs on Objects in Arrays Without a Check (CVE-2024-51754, GHSA-6377-hfv9-hqf6)
Details: https://phpnews.net/security/symfony/ghsa-6377-hfv9-hqf6

Affected versions, as Composer constraints:
- twig/twig: >=1.0.0,<2.0.0|>=2.0.0,<3.0.0|>=3.0.0,<3.11.2|>=3.12.0,<3.14.1

Fixed releases on branches that still get security fixes:
- 3.12.0 – 3.14.0: update to 3.14.1

1. Find every composer.lock in the project outside vendor/ (a monorepo can have one per app) and read the installed version of each package above. Packages installed as dependencies of other packages count too.
2. Compare each installed version with its constraint: "|" separates alternative ranges, and "," means both bounds apply.
3. For each affected install, read "What this means" at https://phpnews.net/security/symfony/ghsa-6377-hfv9-hqf6 and check whether the project meets the conditions it describes (a feature in use, a config value, a driver) (if that page won't load, use https://github.com/advisories/GHSA-6377-hfv9-hqf6). Say which conditions you could check and which you couldn't.
4. Report a table: lock file | package | installed version | affected (yes, no or unknown) | conditions met (yes, no or unknown) | update to | evidence. For each affected package, give the command that would fix it, without running it: composer update <package> --with-dependencies when it is only installed as a dependency of another package, or composer require with the fixed version when composer.json requires it directly. If the installed version is on a branch with no fixed release listed, say it needs a move to a newer branch.

Sources

← All Twig advisories