{"id":"CVE-2026-31951","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-31951","generatedAt":"2026-10-28T05:59:44.852Z","title":"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.","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":"2026-03-27T20:16:30.000Z","lastModified":"2026-10-26T21:10:00.000Z","status":"Analyzed","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":5.7,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N"},"cwe":["CWE-200"],"affected":["librechat/librechat"],"epss":{"score":0.00253,"percentile":0.16762,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.25%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://github.com/danny-avila/LibreChat/security/advisories/GHSA-pmw7-gqwj-f954","tags":["Exploit","Vendor Advisory"],"source":"security-advisories@github.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-31951","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}