{"id":"CVE-2026-73556","title":"vLLM is an inference and serving engine for large language models","summary":"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 compi…","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","cwe":["CWE-400","CWE-1333"],"vendor":"vllm","product":"vllm","affected":["vllm < 0.26.0"],"patched":["vllm 0.26.0"],"published":"2026-08-13","updated":"2026-09-09","sourceUpdated":"2026-09-09T20:58:37.713","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-73556","references":[{"url":"https://github.com/vllm-project/vllm/commit/c9a788eedc412acceaa5112e0d44624b49841577","label":"security-advisories@github.com"},{"url":"https://github.com/vllm-project/vllm/pull/47595","label":"security-advisories@github.com"},{"url":"https://github.com/vllm-project/vllm/releases/tag/v0.26.0","label":"security-advisories@github.com"},{"url":"https://github.com/vllm-project/vllm/security/advisories/GHSA-48jh-3gj7-fg8v","label":"security-advisories@github.com"},{"url":"https://github.com/vllm-project/vllm/security/advisories/GHSA-48jh-3gj7-fg8v","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-73556"},{"url":"https://github.com/advisories/GHSA-48jh-3gj7-fg8v"},{"url":"https://github.com/vllm-project/vllm"},{"url":"https://pypi.org/project/vllm"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-73556.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-73556"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2515404"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-73556"},{"url":"https://access.redhat.com/errata/RHSA-2026:68699"},{"url":"https://access.redhat.com/errata/RHSA-2026:69466"},{"url":"https://access.redhat.com/errata/RHSA-2026:69467"},{"url":"https://access.redhat.com/errata/RHSA-2026:69469"},{"url":"https://access.redhat.com/errata/RHSA-2026:69464"}],"tags":["nvd","ghsa","pip","osv","csaf","vex","red-hat","score-dispute"],"epss":0.00315,"epssPercentile":0.24524,"aliases":["GHSA-48jh-3gj7-fg8v","PYSEC-2026-3933"],"ecosystem":"pip","ingestedAt":"2026-09-04T22:28:54.906Z","scores":{"nvd":5.3,"vendor":7.5},"slug":"CVE-2026-73556","body":"## Overview\n\nvLLM 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-73556)\n\nAffected packages:\n\n- `vllm < 0.26.0`\n\nPatched in:\n\n- `vllm 0.26.0`\n\nSource: https://github.com/advisories/GHSA-48jh-3gj7-fg8v\n\n## Vendor advisories\n\n- **Red Hat VEX** · Important · affected: Red Hat AI Inference Server, Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat OpenShift AI (RHOAI) · no fix planned: Red Hat AI Inference Server, Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat OpenShift AI (RHOAI) · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-73556.json)\n- **RHSA-2026:68699** · Red Hat · fixed in: Red Hat AI Inference Server 3.3 · released 2026-09-17 · [advisory](https://access.redhat.com/errata/RHSA-2026:68699)\n- **RHSA-2026:69466** · Red Hat · fixed in: Red Hat AI Inference Server 3.4 · released 2026-09-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:69466)\n- **RHSA-2026:69467** · Red Hat · fixed in: Red Hat AI Inference Server 3.4 · released 2026-09-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:69467)\n- **RHSA-2026:69469** · Red Hat · fixed in: Red Hat AI Inference Server 3.4 · released 2026-09-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:69469)\n- **RHSA-2026:69464** · Red Hat · fixed in: Red Hat AI Inference Server 3.4 · released 2026-09-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:69464)","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}