Twig: Arbitrary PHP code execution via `_self.(<string>)` macro-reference compilation
The advisory, in context
Description
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.
Resolution
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.
Credits
Twig would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.
Affected packages
Start with the recorded fix for your release branch. Check your installed version and test compatibility before upgrading. Fixing this advisory does not rule out other vulnerabilities in the release.
From 3.15.0 before 3.26.0
Fixed in 3.26.0
15 explicitly affected versions
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
View affected-version evidence
{
"ranges": [
{
"events": [
{
"introduced": "3.15.0"
},
{
"fixed": "3.26.0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"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"
]
}