Summary
Twig: Sandbox property and method bypass via object-destructuring assignment
Description
The object-destructuring assignment syntax introduced in Twig 3.24.0 generates a call to CoreExtension::getAttribute() with the $sandboxed argument hardcoded to false, regardless of whether a SandboxExtension is active. This permanently disables the sandbox's property and method policy checks for every destructuring expression.
ObjectDestructuringSetBinary::compile() emits:
CoreExtension::getAttribute($this->env, $this->source, ..., \Twig\Template::ANY_CALL, false, false, false, ...);
// ^^^^^
// sandbox check never runs
Whereas GetAttrExpression::compile() correctly passes $env->hasExtension(SandboxExtension::class).
An attacker with write access to a sandboxed Twig template can read any public property or invoke any public getter on objects passed to the template engine, bypassing SecurityPolicy restrictions. The exploit requires only the {% do %} tag to be in allowedTags, which is a common configuration.
Resolution
The destructuring compiler now forwards the active sandbox flag to getAttribute() so property/method allowlists are enforced.
Credits
Twig would like to thank Anvil Secure in collaboration with Claude and Anthropic Research for reporting and fixing the issue.
Impact
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-46639? CVE-2026-46639 is a high-severity security vulnerability in twig/twig (composer), affecting versions >= 3.24.0, < 3.26.0. It is fixed in 3.26.0.
- Which versions of twig/twig are affected by CVE-2026-46639? twig/twig (composer) versions >= 3.24.0, < 3.26.0 is affected.
- Is there a fix for CVE-2026-46639? Yes. CVE-2026-46639 is fixed in 3.26.0. Upgrade to this version or later.
- Is CVE-2026-46639 exploitable, and should I be worried? Whether CVE-2026-46639 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-46639 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-46639? Upgrade
twig/twigto 3.26.0 or later.