PT-2026-55213 · Packagist · Twig/Twig
Published
2026-07-01
·
Updated
2026-07-01
·
CVE-2026-49981
CVSS v4.0
8.7
High
| Vector | AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N |
Description
The per-template filter, tag and function allow-list check is compiled into the
checkSecurity() method of each Template subclass and was invoked once from the constructor, gated by SandboxExtension::isSandboxed($source). Template instances are then cached on the Environment in $loadedTemplates, so the verdict computed at construction time was sticky for the rest of the process.Any later change of sandbox state on the same
Environment left that cached verdict in place: toggling SandboxExtension::enableSandbox()/disableSandbox(), swapping the policy via setSecurityPolicy(), a SourcePolicyInterface decision flip, or simply having a parent, macro or included template pre-instantiated outside the sandbox before a sandboxed render reached it. In all of these cases, the filters, tags and functions used by the affected template kept running with the original (typically empty) check, bypassing the SecurityPolicy allow-list.Method, property and
toString allow-lists are not affected: they are enforced at every call site at runtime through SandboxExtension::checkMethodAllowed(), checkPropertyAllowed() and ensureToStringAllowed(), which re-read the current state on every call.Long-lived workers (FrankenPHP, RoadRunner, Symfony Messenger consumers, FPM with hot autoloading) that share a single
Environment between sandboxed and non-sandboxed renders are the most exposed: a single non-sandboxed render of a shared layout pre-warms its Template instance, after which any later sandboxed render that extends, uses, includes or imports from that layout silently skips the filter/tag/function allow-list for the pre-warmed instance.Resolution
The allow-list check is no longer run from the constructor.
Template gains a public ensureSecurityChecked() method that calls the compiled checkSecurity() only when SandboxExtension::isSandboxed($source) returns true for the current source, and it is invoked at every entry point that can reach a Template instance whose security has not yet been verified against the current state: Template::yield(), Template::yieldBlock() (on the resolved block template, which covers extends, use, traits and parent blocks), Template::getParent() (which evaluates user code when the parent name is dynamic) and Template::getTemplateForMacro() (on the resolved macro template).The explicit
checkSecurity() calls previously emitted by IncludeNode and CoreExtension::include() are removed: the included template's own yield() now re-runs the check against the current sandbox state. The compiled checkSecurity() body is a cheap walk over compile-time-static arrays, so the per-render cost is negligible. Old cached compiled PHP files keep working unchanged: the constructor-time call they still contain is idempotent.Credits
Twig would like to thank Fabien Potencier for reporting and fixing the issue.
Fix
Incorrect Authorization
Protection Mechanism Failure
Found an issue in the description? Have something to add? Feel free to write us 👾
Related Identifiers
Affected Products
Twig/Twig