Missing Authentication for Critical Function in LibreChat - CVE-2026-31944
Published: April 27, 2026
Vulnerability identifier: #VU128103
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-31944
CWE-ID: CWE-306
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: LibreChat
Affected software:
LibreChat
LibreChat
Detailed vulnerability description
The vulnerability allows a remote user to steal OAuth tokens and gain unauthorized access to MCP-linked services.
The vulnerability exists due to improper authentication and session validation in the GET /:serverName/oauth/callback endpoint in api/server/routes/mcp.js when processing an OAuth callback redirect. A remote user can send a crafted authorization URL to a victim to steal OAuth tokens and gain unauthorized access to MCP-linked services.
User interaction is required to open the authorization URL, and the issue affects deployments where MCP OAuth is enabled for an integration.
How to mitigate CVE-2026-31944
Install security update from vendor's website.