Symfony's JsonPath Evaluates Attacker-Controlled Regular Expressions in match()/search() Without Limits — ReDoS
Description
The JsonPath component's match() and search() filter functions compile a caller-supplied pattern straight into preg_match():
```php
'match' => @preg_match(\sprintf('/^%s$/u', $this->transformJsonPathRegex($argList[1])), $value),
'search' => @preg_match("/{$this->transformJsonPathRegex($argList[1])}/u", $value),
```
transformJsonPathRegex() only performs cosmetic escaping: there is no length cap, no restriction to the RFC 9485 i-regexp subset, and no bound on backtracking. An application that evaluates an attacker-influenced JSONPath expression server-side (e.g. one taken from a query parameter or API field and passed to JsonCrawler) can therefore be made to run a catastrophic-backtracking pattern such as $[?search(@, "(a+)+$")]. Evaluated against a moderately sized document, this pins a CPU core for seconds per request, so a handful of concurrent requests exhausts the worker pool: a denial of service. Because the preg_match() calls are prefixed with @, the PCRE backtrack-limit errors that would otherwise surface are suppressed, leaving no log trace.
Conditions for exploitation
An application that evaluates an attacker-influenced JSONPath expression containing a match() / search() filter against any non-trivial JSON input.
Resolution
JsonCrawler runs the preg_match() calls through a helper that lowers pcre.backtrack_limit to 10000 for the duration of the call (restoring the previous value afterwards), so a pathological pattern fails fast instead of stalling the worker.
The patch for this issue is available [here](https://github.com/symfony/symfony/commit/1ac2d47418ec23066112db1e6ca35be6fe123d14) for branch 7.4.
Credits
Symfony would like to thank Himanshu Anand for reporting the issue and Alexandre Daubois for providing the fix.
