| Package | Affected versions | Patched versions |
|---|---|---|
| twig/twig | ≥ 3.15.0, < 3.26.0 | 3.26.0 |
| twig | ≥ 3.15.0, < 3.26.0 | 3.26.0 |
The obj.(expr) dynamic-attribute syntax (added in 3.15.0 as the replacement for the deprecated attribute() function) lets the attribute be an arbitrary expression. When the receiver is _self (or any {% import %} alias) and the parenthesised expression is a string literal, DotExpressionParser short-circuits to the macro-call path and concatenates the attacker-controlled string into a MacroReferenceExpression name with no identifier validation. MacroReferenceExpression::compile() then emits that name raw into the generated PHP source.
An attacker who can supply template source can inject arbitrary PHP into the compiled template and execute it at template-load time, before checkSecurity() is ever called. This is a complete bypass of SandboxExtension, including a globally-enabled sandbox with an empty SecurityPolicy allowlist.
The parser now validates that the dynamic attribute resolves to a valid macro identifier before routing through MacroReferenceExpression, and the macro-reference compiler emits the name through a properly escaped path.
Twig would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.
Running one of these products? Scan your site to see whether it exposes a vulnerable version.
Scan my site free