{"id":"CVE-2026-31951","state":"PUBLISHED","title":"LibreChat's MCP Server Header Injection Enables OAuth Token Theft","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.","publishedAt":"2026-03-27T19:29:25.892Z","updatedAt":"2026-03-31T13:46:25.297Z","severity":{"score":6.8,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["danny-avila LibreChat"],"affected":[{"vendor":"danny-avila","product":"LibreChat","versions":[{"version":">= v0.8.2-rc1, <= v0.8.3-rc1","status":"affected"}]}],"references":["https://github.com/danny-avila/LibreChat/security/advisories/GHSA-pmw7-gqwj-f954"],"weaknesses":["CWE-200"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/31xxx/CVE-2026-31951.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-31951","state":"PUBLISHED","datePublished":"2026-03-27T19:29:25.892Z","dateUpdated":"2026-03-31T13:46:25.297Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-03-10T15:10:10.657Z"},"containers":{"cna":{"title":"LibreChat's MCP Server Header Injection Enables OAuth Token Theft","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"danny-avila","product":"LibreChat","versions":[{"version":">= v0.8.2-rc1, <= v0.8.3-rc1","status":"affected"}]}],"references":[{"url":"https://github.com/danny-avila/LibreChat/security/advisories/GHSA-pmw7-gqwj-f954","name":"https://github.com/danny-avila/LibreChat/security/advisories/GHSA-pmw7-gqwj-f954","tags":["x_refsource_CONFIRM"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":6.8,"baseSeverity":"MEDIUM","confidentialityImpact":"HIGH","integrityImpact":"NONE","privilegesRequired":"LOW","scope":"CHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-200","lang":"en","description":"CWE-200: Exposure of Sensitive Information to an Unauthorized Actor","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-03-27T19:29:25.892Z"},"source":{"advisory":"GHSA-pmw7-gqwj-f954","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-03-31T13:45:16.896153Z","id":"CVE-2026-31951","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-03-31T13:46:25.297Z"}}]}}}