GHSA-rwxx-mrjm-wc2m is a high-severity (CVSS 7.5) CWE-1333 vulnerability in vllm. O3 Security confirms whether GHSA-rwxx-mrjm-wc2m is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
vLLM: ReDoS via structured_outputs.regex compiled without timeout in xgrammar and outlines backends
Real-World Exposure
vllmReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The structured_outputs.regex API parameter passes a user-supplied regex string directly to grammar compiler backends with no compilation timeout. In the xgrammar backend, the string reaches compile_regex() with no guard. In the outlines backend, validate_regex_is_buildable() blocks structural issues (lookarounds, backreferences) but provides zero protection against exponential DFA state-space explosion. Patterns like (a+)+b pass all checks and hang the inference worker.
Root Cause
backend_xgrammar.py:91 — no timeout:
ctx = self.compiler.compile_regex(grammar_spec)
backend_outlines.py:299–330 — structural checks only, no complexity analysis:
def validate_regex_is_buildable(regex: str) -> None:
sre_parse.parse(regex) # AST parse only — does not detect exponential patterns
_check_unsupported(...) # blocks lookarounds/backrefs, not nested quantifiers
backend_outlines.py:64 — no timeout:
oc.Index(regex_string, vocabulary.inner)
Impact
Denial of service — one request with an adversarial regex pattern hangs an inference worker indefinitely.
Remediation
Wrap compile_regex() and oc.Index() calls in a thread with a deadline (e.g., 5 seconds). Add complexity analysis to validate_regex_is_buildable() to detect nested quantifier patterns before compilation.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | vllm | all versions | 0.24.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vllm. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update vllm to 0.24.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-rwxx-mrjm-wc2m is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-rwxx-mrjm-wc2m is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-rwxx-mrjm-wc2m. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-rwxx-mrjm-wc2m in your dependencies?
O3 detects GHSA-rwxx-mrjm-wc2m across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.