Twig: template_from_string() escapes a SourcePolicy-driven sandbox via synthesized template name

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

not scored

EPSS

• CVE-2026-46634: 0.62% estimated exploitation activity in the next 30 days; percentile 49.55 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Description When the sandbox is enabled selectively via SourcePolicyInterface (and not globally), a sandboxed template that is allowed to call templatefromstring and include can render an arbitrary inner template with no security policy enforcement. Environment::createTemplate() compiles the inner string under a synthesized name (stringtemplate<hash), so a name/path-based SourcePolicy returns false for it, and the inner template's checkSecurity() becomes a no-op. From a template the integrator believes is sandboxed, an attacker can use any tag/filter/function (including constant() to read secrets, or |map("system") to execute shell commands). Resolution This is a configuration trap rather than a code bug: there is no legitimate use case for exposing templatefromstring to untrusted template authors, and propagating the parent sandbox state through templatefromstring would require invasive changes to SourcePolicyInterface semantics with their own risks. Starting with Twig 3.26.0, the…

Published by the source

21 May 2026, 21:25 UTC

Last modified by the source

21 May 2026, 21:25 UTC

Source last checked

26 Oct 2026, 14:40 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-24x9-r6q4-q93w

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# Patch Next advisory brief: CVE-2026-46634

Advisory: Twig: `template_from_string()` escapes a SourcePolicy-driven sandbox via synthesized template name
IDs: CVE-2026-46634, GHSA-24x9-r6q4-q93w
Record: https://patchnext.com/advisories/cve-2026-46634 (revision 1, source checked 26 Oct 2026, 14:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: twig/twig 3.26.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist twig/twig: affected >= 3.9.0, < 3.26.0; fixed in 3.26.0

## Suggested inspection (read-only)
- Packagist twig/twig: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on twig/twig.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-24x9-r6q4-q93w (GitHub-reviewed advisory GHSA-24x9-r6q4-q93w lists affected ranges: Packagist twig/twig >=3.9.0 <3.26.0)

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