{"id":"CVE-2026-31951","summary":"LibreChat's MCP Server Header Injection Enables OAuth Token Theft","details":"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.","aliases":["GHSA-pmw7-gqwj-f954"],"modified":"2026-08-12T03:51:40.544782252Z","published":"2026-03-27T19:29:25.892Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31951.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-200"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31951.json"},{"type":"ADVISORY","url":"https://github.com/danny-avila/LibreChat/security/advisories/GHSA-pmw7-gqwj-f954"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31951"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/danny-avila/librechat","events":[{"introduced":"efbc088642afb69540efae9518b66e07760b23b7"},{"fixed":"cfbe812d63451c1578faa9a13b7e77e0c9a9789b"},{"introduced":"9eeec6bc4f5e856ac65f50784254d484b2808622"},{"last_affected":"9eeec6bc4f5e856ac65f50784254d484b2808622"}],"database_specific":{"cpe":["cpe:2.3:a:librechat:librechat:*:*:*:*:*:*:*:*","cpe:2.3:a:librechat:librechat:0.8.3:rc1:*:*:*:*:*:*"],"extracted_events":[{"introduced":"0.8.2"},{"fixed":"0.8.3"},{"introduced":"0.8.3-rc1"},{"last_affected":"0.8.3-rc1"}],"source":["CPE_RANGE","CPE_STRING"]}}],"versions":["0.8.3-rc1","v0.8.3-rc2","chart-1.9.9","v0.8.3-rc1","chart-1.9.8"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31951.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N"}]}