{"id":"CVE-2026-73556","aliases":["GHSA-48jh-3gj7-fg8v"],"url":"https://o3.security/vulnerability/CVE-2026-73556","summary":"vLLM: ReDoS via structured_outputs.regex in the lm-format-enforcer backend (no compile timeout) — missed sibling of CVE-2026-55574","details":"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.","published":"2026-08-13T14:56:52.569Z","modified":"2026-08-16T03:31:00.692996663Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"PyPI","name":"vllm","fixedVersion":"0.26.0"}],"fix":{"url":"https://github.com/vllm-project/vllm/commit/c9a788eedc412acceaa5112e0d44624b49841577","label":"vllm-project/vllm@c9a788e"},"references":[{"type":"WEB","url":"https://github.com/vllm-project/vllm/releases/tag/v0.26.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73556.json"},{"type":"ADVISORY","url":"https://github.com/vllm-project/vllm/security/advisories/GHSA-48jh-3gj7-fg8v"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-73556"},{"type":"FIX","url":"https://github.com/vllm-project/vllm/commit/c9a788eedc412acceaa5112e0d44624b49841577"},{"type":"FIX","url":"https://github.com/vllm-project/vllm/pull/47595"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-16T03:31:00.692996663Z"}}