CVE-2026-46634 — twig/twig
Fix: twigphp/Twig@1cde8f2CVE-2026-46634 is a CWE-693 vulnerability in twig/twig. A fix is available for twig/twig — see the affected versions and patch details below.
Twig: `template_from_string()` escapes a SourcePolicy-driven sandbox via synthesized template name
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-46634.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
Real-World Exposure
twig/twigReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Description
When the sandbox is enabled selectively via SourcePolicyInterface (and not globally), a sandboxed template that is allowed to call template_from_string and include can render an arbitrary inner template with no security policy enforcement.
Environment::createTemplate() compiles the inner string under a synthesized name (__string_template__<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 template_from_string to untrusted template authors, and propagating the parent sandbox state through template_from_string would require invasive changes to SourcePolicyInterface semantics with their own risks.
Starting with Twig 3.26.0, the documentation and the PHPDoc of StringLoaderExtension::templateFromString() explicitly warn against allowing template_from_string in a sandboxed environment (i.e. listing it in a SecurityPolicy allowed-functions list). Integrators using a SourcePolicyInterface MUST NOT allow template_from_string in their allowed functions; the safest option is not to register StringLoaderExtension at all when a sandbox is in use.
Credits
Twig would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | twig/twig | ≥ 3.9.0&&< 3.26.0 | 3.26.0composer require twig/twig:^3.26.0 |
Affected Products
twigsymfonyDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for twig/twig, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update twig/twig to 3.26.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-46634 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2026-46634 in your dependencies?
Find it across Packagist, including transitive dependencies.