CVE-2026-47732

Description

SandboxNodeVisitor enforces SecurityPolicy::checkMethodAllowed() for implicit __toString() calls by wrapping selected AST nodes in CheckToStringNode. The set of wrapped nodes is incomplete, and several Twig language constructs still trigger PHP string coercion on a Stringable operand without first consulting the policy. A sandboxed template author can therefore invoke __toString() on any object reachable in the render context, even when __toString on its class is not allowlisted.

Confirmed bypass vectors:

• Conditional expressions (a ? b : c, a ?: b, a ?? b) used as the input of a string-coercing filter or as a filter/function argument.
• The matches operator and the loose comparison operators (==, !=, <, >, <=, >=, <=>), which coerce a Stringable operand to string and can be used as an oracle to recover the value byte by byte (no tag, filter or function needs to be allowlisted).
• Twig tests in general (which were never policy-gated), in particular is empty which casts a Stringable value via (string) $value in CoreExtension::testEmpty().
• Null-coalesce expressions nested in concatenation, and the direct output of allowed functions or filters that return a Stringable object.
• Arguments passed to allowed object methods, template-name expressions of template-loading tags (include, extends, use, ...), dynamic attribute/property names, and spread arguments from Traversable objects.
• The do tag and the .. range operator.

Resolution

The sandbox now wraps every child node that the parent will string-coerce at runtime, instead of relying on a hardcoded list of node types in SandboxNodeVisitor. A new Twig\Node\CoercesChildrenToStringInterface lets nodes declare which of their children must be guarded; core nodes (concatenation, comparison and range binaries, filter/function/test expressions, do, include, extends, use, ...) implement it. Spread arguments are materialised and policy-checked via the new SandboxExtension::ensureSpreadAllowed(), and dynamic attribute names are checked at runtime inside CoreExtension::getAttribute().

Credits

Twig would like to thank Anthropic Glasswing and El Kharoubi Iosif for reporting the issues, and Fabien Potencier for providing the fixes.

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

Kodem intelligence

1. What is CVE-2026-47732? CVE-2026-47732 is a high-severity improper input validation vulnerability in twig/twig (composer), affecting versions <= 3.25.0. It is fixed in 3.26.0. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
2. Which versions of twig/twig are affected by CVE-2026-47732? twig/twig (composer) versions <= 3.25.0 is affected.
3. Is there a fix for CVE-2026-47732? Yes. CVE-2026-47732 is fixed in 3.26.0. Upgrade to this version or later.
4. Is CVE-2026-47732 exploitable, and should I be worried? Whether CVE-2026-47732 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
5. What actually determines whether CVE-2026-47732 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.
6. How do I fix CVE-2026-47732? Upgrade twig/twig to 3.26.0 or later.