## 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_spec) ``` `backend_outlines.py:299–330` — structural checks only, no complexity analysis: ```python 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: ```python 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.
## 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_spec) ``` `backend_outlines.py:299–330` — structural checks only, no complexity analysis: ```python 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: ```python 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.
Update vllm to 0.24.0 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanvLLM: ReDoS via structured_outputs.regex compiled without timeout in xgrammar and outlines backends affects vllm (pip). Severity is high. ## 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_spec) ``` `backend_outlines.py:299–330` — structural checks only, no complexity analysis: ```python 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: ```python 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.
AI coding agents often install or upgrade packages automatically in pip. A high vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
| vllmpip | <0.24.0 | 0.24.0 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL GuardUpdate vllm to 0.24.0 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanvLLM: ReDoS via structured_outputs.regex compiled without timeout in xgrammar and outlines backends affects vllm (pip). Severity is high. ## 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_spec) ``` `backend_outlines.py:299–330` — structural checks only, no complexity analysis: ```python 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: ```python 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.
AI coding agents often install or upgrade packages automatically in pip. A high vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
| vllmpip | <0.24.0 | 0.24.0 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL Guard