CVE-2026-48806

Description

This is a residual bypass of CVE-2026-47732 / GHSA-pr2w-4gpj-cpq4 left after the initial fix for unguarded __toString() calls.

In 3.26.0 the sandbox visitor was extended to wrap every child node that its parent will string-coerce at runtime with CheckToStringNode, gated by the new CoercesChildrenToStringInterface. ArrayExpression did not implement the interface for its mapping keys: when a dynamic key expression resolves to a Stringable object, ArrayExpression::compile() emits a raw (string) cast (via StringCastUnary for ContextVariable keys, and no cast at all for richer key expressions). PHP then invokes __toString() directly, without ever calling SandboxExtension::ensureToStringAllowed().

A sandboxed template author can therefore trigger __toString() on any object reachable in the render context by using it as a dynamic mapping key, for example:

{% set arr = {(obj): "value"} %}

Direct output of the same object is correctly blocked, which makes this a clear policy enforcement gap. The reliable demonstrated impact is unauthorised disclosure of data returned by __toString().

Resolution

ArrayExpression now declares its dynamic mapping keys as string-coercion sites through CoercesChildrenToStringInterface, so the sandbox visitor wraps them with CheckToStringNode and the policy is consulted before PHP coerces the key to a string. The compiler also keeps an explicit (string) cast around the wrapped expression so PHP type errors on non-string keys are preserved.

As a side effect, any expression is now accepted as a dynamic mapping key (not only context variables); this is documented as a new feature on the 3.x branch.

Credits

Twig would like to thank El Kharoubi Iosif for reporting the issue and Fabien Potencier for providing the fix.

The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.

Kodem intelligence

1. What is CVE-2026-48806? CVE-2026-48806 is a medium-severity incorrect authorization vulnerability in twig/twig (composer), affecting versions <= 3.26.0. It is fixed in 3.27.0. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
2. Which versions of twig/twig are affected by CVE-2026-48806? twig/twig (composer) versions <= 3.26.0 is affected.
3. Is there a fix for CVE-2026-48806? Yes. CVE-2026-48806 is fixed in 3.27.0. Upgrade to this version or later.
4. Is CVE-2026-48806 exploitable, and should I be worried? Whether CVE-2026-48806 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-2026-48806 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-2026-48806? Upgrade twig/twig to 3.27.0 or later.