Authorization and Authentication Flaws in Obsidian Web MCP Remote Server

CVE-2026-54618

What is CVE-2026-54618?

The Obsidian Web MCP, a remote server for Obsidian vaults, has serious weaknesses in its OAuth implementation prior to version 0.2.0. It allows unauthorized access by issuing an authorization code without requiring user login or consent, meaning an attacker can manipulate critical vault functions without authentication. Additionally, the option for PKCE does not mitigate this risk, as the protocol can still be leveraged by unauthorized users. An unauthenticated remote caller with access to the tunnel deployment can exploit these flaws to execute commands that could read, write, move, or delete vault data. Furthermore, the lack of client authentication during the token exchange process poses an additional risk by exposing sensitive client secrets. These issues have been addressed in the latest version of the product.

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