CVE-2026-49981: Twig sandbox allow-list bypass via template cache reuse

CVE-2026-49981 · Severity: high · CVSS 4 · Published 2026-07-14

Twig, a popular template engine for PHP, contains a security flaw in its sandbox mode. The sandbox is designed to safely run untrusted code by restricting which functions and tags can be used; however, a caching error allows these restrictions to be bypassed if the system switches between sandboxed and non-sandboxed modes. This could allow an attacker with limited access to execute unauthorized functions, potentially leading to data exposure or unauthorized actions within the application.

Technologies: twig/twig (Packagist). Vendors: Packagist.

Quick answers

Is CVE-2026-49981 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-49981 being exploited in the wild.
How severe is CVE-2026-49981?
High severity, with a CVSS score of 4, published 14 July 2026.
Which products and versions are affected?
twig/twig (Packagist) <= 3.26.0, ECOSYSTEM:introduced=0,fixed=3.27.0.
Is there a fix for CVE-2026-49981?
Yes. twig/twig (Packagist): upgrade to 3.27.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-49981 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-49981?
Check whether you run twig/twig (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • twig/twig (Packagist): upgrade to 3.27.0 or later
    composer require twig/twig:^3.27.0

Technical details

A vulnerability in Twig's sandbox mechanism exists where the allow-list verdict for filters, tags, and functions is computed during Template construction and cached. Because Template instances are stored in the Environment's $loadedTemplates cache, the security verdict remains 'sticky' even if the sandbox state changes (e.g., enabling/disabling the sandbox or swapping security policies). In environments with long-lived workers (like FrankenPHP or RoadRunner), a template pre-warmed in a non-sandboxed context can be reused in a sandboxed context without re-verifying the security policy. This allows an attacker to bypass SecurityPolicy restrictions. The fix in version 3.27.0 moves the security check from the constructor to a new ensureSecurityChecked() method called during template execution.

Affected products

  • twigphp Twig < 3.27.0

Identifiers

  • CVE-2026-49981
  • GHSA-529h-vh3j-85hq

Timeline

  • 2026-05-27: patched: Version 3.27.0 released
  • 2026-05-27: advisory: GitHub Security Advisory published
  • 2026-07-14: disclosed: NVD publication date

References

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