CVE-2026-31951: Librechat

Medium severity, CVSS 5.7. EPSS: 0.4% chance of exploitation in the next 30 days.

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 products

• Librechat Librechat: from 0.8.2, before 0.8.3 (fixed in 0.8.3); version 0.8.3 only

Published 2026-03-27. Last modified 2026-06-17.