{"id":"CVE-2026-73556","state":"PUBLISHED","title":"vLLM: ReDoS via structured_outputs.regex in the lm-format-enforcer backend (no compile timeout) — missed sibling of CVE-2026-55574","description":"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.","publishedAt":"2026-08-13T14:56:52.569Z","updatedAt":"2026-08-14T16:52:40.458Z","severity":{"score":5.3,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","source":"GitHub_M"},"assigner":"GitHub_M","products":["vllm-project vllm"],"affected":[{"vendor":"vllm-project","product":"vllm","versions":[{"version":"< 0.26.0","status":"affected"}]}],"references":["https://github.com/vllm-project/vllm/security/advisories/GHSA-48jh-3gj7-fg8v","https://github.com/vllm-project/vllm/pull/47595","https://github.com/vllm-project/vllm/commit/c9a788eedc412acceaa5112e0d44624b49841577","https://github.com/vllm-project/vllm/releases/tag/v0.26.0"],"weaknesses":["CWE-400","CWE-1333"],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/73xxx/CVE-2026-73556.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-73556","state":"PUBLISHED","datePublished":"2026-08-13T14:56:52.569Z","dateUpdated":"2026-08-14T16:52:40.458Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-08-12T20:53:46.380Z"},"containers":{"cna":{"title":"vLLM: ReDoS via structured_outputs.regex in the lm-format-enforcer backend (no compile timeout) — missed sibling of CVE-2026-55574","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"vllm-project","product":"vllm","versions":[{"version":"< 0.26.0","status":"affected"}]}],"references":[{"url":"https://github.com/vllm-project/vllm/security/advisories/GHSA-48jh-3gj7-fg8v","name":"https://github.com/vllm-project/vllm/security/advisories/GHSA-48jh-3gj7-fg8v","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/vllm-project/vllm/pull/47595","name":"https://github.com/vllm-project/vllm/pull/47595","tags":["x_refsource_MISC"]},{"url":"https://github.com/vllm-project/vllm/commit/c9a788eedc412acceaa5112e0d44624b49841577","name":"https://github.com/vllm-project/vllm/commit/c9a788eedc412acceaa5112e0d44624b49841577","tags":["x_refsource_MISC"]},{"url":"https://github.com/vllm-project/vllm/releases/tag/v0.26.0","name":"https://github.com/vllm-project/vllm/releases/tag/v0.26.0","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":5.3,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-400","lang":"en","description":"CWE-400: Uncontrolled Resource Consumption","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-1333","lang":"en","description":"CWE-1333: Inefficient Regular Expression Complexity","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-08-13T14:56:52.569Z"},"source":{"advisory":"GHSA-48jh-3gj7-fg8v","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/vllm-project/vllm/security/advisories/GHSA-48jh-3gj7-fg8v","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-14T16:52:13.326454Z","id":"CVE-2026-73556","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-14T16:52:40.458Z"}}]}}}