{"id":"GHSA-24x9-r6q4-q93w","summary":"Twig: `template_from_string()` escapes a SourcePolicy-driven sandbox via synthesized template name","details":"### Description\n\nWhen the sandbox is enabled selectively via `SourcePolicyInterface` (and not globally), a sandboxed template that is allowed to call `template_from_string` and `include` can render an arbitrary inner template with no security policy enforcement.\n\n`Environment::createTemplate()` compiles the inner string under a synthesized name (`__string_template__\u003chash\u003e`), so a name/path-based `SourcePolicy` returns `false` for it, and the inner template's `checkSecurity()` becomes a no-op. From a template the integrator believes is sandboxed, an attacker can use any tag/filter/function (including `constant()` to read secrets, or `|map(\"system\")` to execute shell commands).\n\n### Resolution\n\nThis is a configuration trap rather than a code bug: there is no legitimate use case for exposing `template_from_string` to untrusted template authors, and propagating the parent sandbox state through `template_from_string` would require invasive changes to `SourcePolicyInterface` semantics with their own risks.\n\nStarting with Twig 3.26.0, the documentation and the PHPDoc of `StringLoaderExtension::templateFromString()` explicitly warn against allowing `template_from_string` in a sandboxed environment (i.e. listing it in a `SecurityPolicy` allowed-functions list). Integrators using a `SourcePolicyInterface` MUST NOT allow `template_from_string` in their allowed functions; the safest option is not to register `StringLoaderExtension` at all when a sandbox is in use.\n\n### Credits\n\nTwig would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue.","aliases":["CVE-2026-46634"],"modified":"2026-09-10T03:51:04.122036504Z","published":"2026-05-21T21:25:12Z","database_specific":{"nvd_published_at":null,"cwe_ids":["CWE-693"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-05-21T21:25:12Z"},"references":[{"type":"WEB","url":"https://github.com/twigphp/Twig/security/advisories/GHSA-24x9-r6q4-q93w"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/twig/twig/CVE-2026-46634.yaml"},{"type":"PACKAGE","url":"https://github.com/twigphp/Twig"},{"type":"WEB","url":"https://symfony.com/cve-2026-46634"}],"affected":[{"package":{"name":"twig/twig","ecosystem":"Packagist","purl":"pkg:composer/twig/twig"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.9.0"},{"fixed":"3.26.0"}]}],"versions":["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","v3.20.0","v3.21.0","v3.21.1","v3.22.0","v3.22.1","v3.22.2","v3.23.0","v3.24.0","v3.25.0","v3.9.0","v3.9.1","v3.9.2","v3.9.3"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-24x9-r6q4-q93w/GHSA-24x9-r6q4-q93w.json"}}],"schema_version":"1.9.0"}