GHSA-hrwp-4hh9-c8r8

Описание

Summary

The Volt template compiler in Phalcon generates the PHP for the join filter by string-concatenating the filter's raw template-literal argument bytes with no escaping. The separator literal is dropped verbatim between two single quotes the compiler emits, and the piped array argument is emitted completely bare. A Volt template whose join arguments are attacker-influenced can therefore break out of the generated join('…') call and inject arbitrary PHP into the compiled template. Volt writes that compiled template to a cache file and require()s it at render time, so the injected PHP executes i.e. compile-time PHP code injection (server-side template injection -> remote code execution) for any application that compiles attacker-controlled Volt source.

Details

Root cause

phalcon/Mvc/View/Engine/Volt/Compiler.zep:2544-2546:

funcArguments[1]["expr"]["value"] (the separator) and funcArguments[0]["expr"]["value"] (the piped array) are the raw values of the parsed template tokens. Unlike every other expression in the compiler, they are not routed through expression() and receive no escaping: the separator value is spliced verbatim inside the join(' … ' quotes with no neutralisation of ', and the array value is emitted with no quoting at all. Volt's scanner stores string-literal bytes verbatim (escape sequences are not decoded), so attacker bytes survive intact into the generated PHP.

Generated-C ground truth -> build/phalcon/phalcon.zep.c (Phalcon 5.15.0):

i.e. literally "join('" + separator + "', " + array + ")" with both attacker-controlled fragments unescaped.

The compiled output is then written to a cache file and required by Phalcon\Mvc\View\Engine\Volt::render(), so any PHP spliced in by the attacker runs at render time.

PoC

Impact

Where an application compiles Volt source that is wholly or partly attacker-controlled, this yields remote code execution in the web-server process.