Vulnerability · Published Jul 6, 2026 · Assigned by GitHub_M
CVE-2026-55574vLLM: ReDoS via structured_outputs.regex compiled without timeout in xgrammar and outlines backends
High 8.7
In plain English
A high-severity regular-expression denial of service in vllm from vllm-project. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 48% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
vLLM is a high-throughput and memory-efficient inference and serving engine for LLMs. Prior to 0.24.0, the structured_outputs.regex API parameter passes a user-supplied regular expression string directly to the grammar compiler backends with no compilation timeout; in the xgrammar backend the string reaches the regex compiler with no guard, and in the outlines backend the validation step blocks structural issues such as lookarounds and backreferences but performs no complexity analysis, so a pattern with nested quantifiers passes all checks and causes exponential state-space expansion, allowing a single request containing an adversarial regex to hang an inference worker indefinitely and deny service. This issue is fixed in version 0.24.0.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | vllm | 0.24.0 | GHSA-rwxx-mrjm-wc2m |
| PyPI | vllm | 0.24.0 | PYSEC-2026-2304 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| vllm-project | vllm | < 0.24.0 |
Weakness: CWE-1333 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
References
- https://github.com/vllm-project/vllm/security/advisories/GHSA-rwxx-mrjm-wc2m x_refsource_CONFIRM
- https://github.com/vllm-project/vllm/pull/45118 x_refsource_MISC
- https://github.com/vllm-project/vllm/commit/2b3006076c5e9bc4cda9e03e3641388de3c5c286 x_refsource_MISC