Twig: Sandbox __toString() policy bypass via dynamic mapping keys

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

not scored

EPSS

• CVE-2026-48806: 0.42% estimated exploitation activity in the next 30 days; percentile 36.18 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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: Direct output of the same object is correctly blocked, which makes this a clear policy enforcement gap. The reliable demonstrated…

Published by the source

30 Jun 2026, 18:42 UTC

Last modified by the source

30 Jun 2026, 18:42 UTC

Source last checked

26 Oct 2026, 14:49 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-5v5v-ww74-355v

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# Patch Next advisory brief: CVE-2026-48806

Advisory: Twig: Sandbox `__toString()` policy bypass via dynamic mapping keys
IDs: CVE-2026-48806, GHSA-5v5v-ww74-355v
Record: https://patchnext.com/advisories/cve-2026-48806 (revision 1, source checked 26 Oct 2026, 14:49 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: twig/twig 3.27.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist twig/twig: affected <= 3.26.0; fixed in 3.27.0

## Suggested inspection (read-only)
- Packagist twig/twig: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on twig/twig.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5v5v-ww74-355v (GitHub-reviewed advisory GHSA-5v5v-ww74-355v lists affected ranges: Packagist twig/twig >=0 <=3.26.0)

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