{"identifier":"CVE-2026-31951","cve":{"id":"CVE-2026-31951","description":"LibreChat is a ChatGPT clone with additional features. In versions 0.8.2-rc1 through 0.8.3-rc1, user-created MCP (Model Context Protocol) servers can include arbitrary HTTP headers that undergo credential placeholder substitution. An attacker can create a malicious MCP server with headers containing `{{LIBRECHAT_OPENID_ACCESS_TOKEN}}` (and others), causing victims who call tools on that server to have their OAuth tokens exfiltrated. Version 0.8.3-rc2 fixes the issue.","published":"2026-03-27T20:16:30.397000+00:00","modified":"2026-10-26T21:10:00.170000+00:00","status":"Analyzed","score":6.8,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N","cvss_version":"3.1","affected":[{"criteria":"cpe:2.3:a:librechat:librechat:*:*:*:*:*:*:*:*","versionStartIncluding":"0.8.2","versionStartExcluding":"","versionEndIncluding":"","versionEndExcluding":"0.8.3"},{"criteria":"cpe:2.3:a:librechat:librechat:0.8.3:rc1:*:*:*:*:*:*","versionStartIncluding":"","versionStartExcluding":"","versionEndIncluding":"","versionEndExcluding":""}],"weaknesses":["CWE-200"],"references":[{"url":"https://github.com/danny-avila/LibreChat/security/advisories/GHSA-pmw7-gqwj-f954","source":"security-advisories@github.com","tags":["Exploit","Vendor Advisory"]}],"kev":null,"kev_checked":true,"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N","baseScore":6.8,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"REQUIRED","scope":"CHANGED","confidentialityImpact":"HIGH","integrityImpact":"NONE","availabilityImpact":"NONE"},"exploitabilityScore":2.3,"impactScore":4.0},{"source":"nvd@nist.gov","type":"Primary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N","baseScore":5.7,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"NONE","availabilityImpact":"NONE"},"exploitabilityScore":2.1,"impactScore":3.6}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-03-31T13:45:16.896153Z","id":"CVE-2026-31951","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:librechat:librechat:*:*:*:*:*:*:*:*","versionStartIncluding":"0.8.2","versionEndExcluding":"0.8.3","matchCriteriaId":"0B0F03AD-B51B-4501-B292-3133DBD964A8"},{"vulnerable":true,"criteria":"cpe:2.3:a:librechat:librechat:0.8.3:rc1:*:*:*:*:*:*","matchCriteriaId":"482D0FE3-2AB3-47B6-982E-564A5B824464"}]}]}],"source":"nvd","retrieved_at":"2026-10-28T10:18:20.990780+00:00","exploited":false,"kev_stale":false,"products":["librechat / librechat"],"priority":{"label":"Assess exposure and vendor guidance","reasons":["No higher-priority signal is available in the current stored evidence."]},"epss":{"probability":0.00253,"percentile":0.16872,"date":"2026-10-29","stale":false},"version_assessment":null},"news":[],"campaigns":[],"domains":[{"domain":"github.com","source_url":"https://github.com/danny-avila/LibreChat/security/advisories/GHSA-pmw7-gqwj-f954","investigate_url":"https://investigate.aeglixmind.com/#github.com"}],"arsenal_url":"https://arsenal.aeglixmind.com/?cve=CVE-2026-31951","catalog_url":"https://cves.aeglixmind.com/cve/CVE-2026-31951","research_url":"https://investigate.aeglixmind.com/research/cve/CVE-2026-31951","coverage":{"news_candidates_checked":0,"campaign_candidates_checked":0,"bounded":false,"notice":"Exact CVE mentions in stored public excerpts and reviewed campaign content only. A mention is not proof of exploitation, attribution or tool suitability. Missing matches do not establish absence."}}