Medium 5.3Published Aug 13, 2026

CVE-2026-73556vLLM: ReDoS via structured_outputs.regex in the lm-format-enforcer backend (no compile timeout) — missed sibling of CVE-2026-55574

Updated under an hour ago (2026-10-19 07:10 UTC)

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It affects vllm-project vllm and 1 other product. Add what you run to find out whether that includes you.

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Every CVE for vllm-project vllm

Exploited in the last 30 days

vLLM is an inference and serving engine for large language models. Prior to 0.26.0, the structured_outputs.regex parameter in vllm/v1/structured_output/backend_lm_format_enforcer.py is passed to lmformatenforcer.RegexParser without compile_regex_with_timeout or validation in validate_structured_output_request_lm_format_enforcer, allowing an unauthenticated /v1/completions request against the lm-format-enforcer backend to consume a CPU core and stall the structured-output engine path with a catastrophic regular expression. This issue is fixed in version 0.26.0.

CVSS: 5.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness (CWE): CWE-400, CWE-1333
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Aug 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

vllm-project vllm vllm_project:vllm (from the name)	before 0.26.0	CNA record
vllm vllm vllm:vllm	before 0.26.0	NVD

References

https://github.com/vllm-project/vllm/security/advisories/GHSA-48jh-3gj7-fg8vx-refsource-confirm, vendor-advisory
https://github.com/vllm-project/vllm/pull/47595x-refsource-misc, issue-tracking, patch
https://github.com/vllm-project/vllm/commit/c9a788eedc412acceaa5112e0d44624b49841577x-refsource-misc, patch
https://github.com/vllm-project/vllm/releases/tag/v0.26.0x-refsource-misc, release-notes

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.