{"id":"GHSA-5v5v-ww74-355v","summary":"Twig: Sandbox `__toString()` policy bypass via dynamic mapping keys","details":"### Description\n\nThis is a residual bypass of CVE-2026-47732 / GHSA-pr2w-4gpj-cpq4 left after the initial fix for unguarded `__toString()` calls.\n\nIn 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()`.\n\nA 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:\n\n```twig\n{% set arr = {(obj): \"value\"} %}\n```\n\nDirect 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()`.\n\n### Resolution\n\n`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.\n\nAs 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.\n\n### Credits\n\nTwig would like to thank El Kharoubi Iosif for reporting the issue and Fabien Potencier for providing the fix.","aliases":["CVE-2026-48806"],"modified":"2026-08-24T00:36:53.585842208Z","published":"2026-06-30T18:42:49Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2026-06-30T18:42:49Z","nvd_published_at":null,"cwe_ids":["CWE-693","CWE-863"],"severity":"MODERATE"},"references":[{"type":"WEB","url":"https://github.com/twigphp/Twig/security/advisories/GHSA-5v5v-ww74-355v"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/twig/twig/CVE-2026-48806.yaml"},{"type":"PACKAGE","url":"https://github.com/twigphp/Twig"},{"type":"WEB","url":"https://github.com/twigphp/Twig/releases/tag/v3.27.0"},{"type":"WEB","url":"https://symfony.com/blog/cve-2026-48806-sandbox-tostring-policy-bypass-via-dynamic-mapping-keys"}],"affected":[{"package":{"name":"twig/twig","ecosystem":"Packagist","purl":"pkg:composer/twig/twig"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.27.0"}]}],"versions":["1.3.0","1.4.0","1.5.0","1.5.1","1.6.0","1.6.1","1.6.2","1.6.3","1.6.4","1.6.5","v1.10.0","v1.10.1","v1.10.2","v1.10.3","v1.11.0","v1.11.1","v1.12.0","v1.12.0-RC1","v1.12.1","v1.12.2","v1.12.3","v1.13.0","v1.13.1","v1.13.2","v1.14.0","v1.14.1","v1.14.2","v1.15.0","v1.15.1","v1.16.0","v1.16.1","v1.16.2","v1.16.3","v1.17.0","v1.18.0","v1.18.1","v1.18.2","v1.19.0","v1.20.0","v1.21.0","v1.21.1","v1.21.2","v1.22.0","v1.22.1","v1.22.2","v1.22.3","v1.23.0","v1.23.1","v1.23.2","v1.23.3","v1.24.0","v1.24.1","v1.24.2","v1.25.0","v1.26.0","v1.26.1","v1.27.0","v1.28.0","v1.28.1","v1.28.2","v1.29.0","v1.30.0","v1.31.0","v1.32.0","v1.33.0","v1.33.1","v1.33.2","v1.34.0","v1.34.1","v1.34.2","v1.34.3","v1.34.4","v1.35.0","v1.35.1","v1.35.2","v1.35.3","v1.35.4","v1.36.0","v1.37.0","v1.37.1","v1.38.0","v1.38.1","v1.38.2","v1.38.3","v1.38.4","v1.39.0","v1.39.1","v1.40.0","v1.40.1","v1.41.0","v1.42.0","v1.42.1","v1.42.2","v1.42.3","v1.42.4","v1.42.5","v1.43.0","v1.43.1","v1.44.0","v1.44.1","v1.44.2","v1.44.3","v1.44.4","v1.44.5","v1.44.6","v1.44.7","v1.44.8","v1.7.0","v1.8.0","v1.8.1","v1.8.2","v1.8.3","v1.9.0","v1.9.1","v1.9.2","v2.0.0","v2.1.0","v2.10.0","v2.11.0","v2.11.1","v2.11.2","v2.11.3","v2.12.0","v2.12.1","v2.12.2","v2.12.3","v2.12.4","v2.12.5","v2.13.0","v2.13.1","v2.14.0","v2.14.1","v2.14.10","v2.14.11","v2.14.12","v2.14.13","v2.14.2","v2.14.3","v2.14.4","v2.14.5","v2.14.6","v2.14.7","v2.14.8","v2.14.9","v2.15.0","v2.15.1","v2.15.2","v2.15.3","v2.15.4","v2.15.5","v2.15.6","v2.16.0","v2.16.1","v2.2.0","v2.3.0","v2.3.1","v2.3.2","v2.4.0","v2.4.1","v2.4.2","v2.4.3","v2.4.4","v2.4.5","v2.4.6","v2.4.7","v2.4.8","v2.5.0","v2.6.0","v2.6.1","v2.6.2","v2.7.0","v2.7.1","v2.7.2","v2.7.3","v2.7.4","v2.8.0","v2.8.1","v2.9.0","v3.0.0","v3.0.0-BETA1","v3.0.1","v3.0.2","v3.0.3","v3.0.4","v3.0.5","v3.1.0","v3.1.1","v3.10.0","v3.10.1","v3.10.2","v3.10.3","v3.11.0","v3.11.1","v3.11.2","v3.11.3","v3.12.0","v3.13.0","v3.14.0","v3.14.1","v3.14.2","v3.15.0","v3.16.0","v3.17.0","v3.17.1","v3.18.0","v3.19.0","v3.2.1","v3.20.0","v3.21.0","v3.21.1","v3.22.0","v3.22.1","v3.22.2","v3.23.0","v3.24.0","v3.25.0","v3.26.0","v3.3.0","v3.3.1","v3.3.10","v3.3.2","v3.3.3","v3.3.4","v3.3.5","v3.3.6","v3.3.7","v3.3.8","v3.3.9","v3.4.0","v3.4.1","v3.4.2","v3.4.3","v3.5.0","v3.5.1","v3.6.0","v3.6.1","v3.7.0","v3.7.1","v3.8.0","v3.9.0","v3.9.1","v3.9.2","v3.9.3"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-5v5v-ww74-355v/GHSA-5v5v-ww74-355v.json","last_known_affected_version_range":"\u003c= 3.26.0"}}],"schema_version":"1.9.0"}