SOURCE-LINKED INTELLIGENCE

GHSA-rwxx-mrjm-wc2m: vLLM: ReDoS via structured_outputs.regex compiled without timeout in xgrammar and outlines backends

OSV AI package advisories · observation · Jul 6, 2026 · UTC

## 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: ```python ctx = self.compiler.compile_regex(grammar_s

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recordType

vulnerability

status

active

evidenceStatus

reported

region

Global