CVE-2026-31944: LibreChat MCP OAuth callback stores tokens for the wrong user

Summary

LibreChat versions 0.8.2 through 0.8.2-rc3 have a flaw in the MCP (Model Context Protocol) OAuth callback endpoint. It stores OAuth tokens for the user who started the flow without checking that the browser completing the redirect is logged in or belongs to that same user. An attacker can send a victim the authorization URL, and the victim's tokens for linked services such as Atlassian and Outlook end up on the attacker's account, enabling account takeover.

Mitigation

Fixed in 0.8.3-rc1.

Topics

• Model Context Protocol

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