CVE-2026-54618

Name of the Vulnerable Software and Affected Versions Obsidian Web MCP versions prior to 0.2.0

Description An authentication bypass exists where the '/oauth/authorize' endpoint issues an authorization code without requiring login, consent, or a session check. Subsequently, the '/oauth/token' endpoint allows the exchange of this code for the static VAULT MCP TOKEN without client authentication. This enables an unauthenticated remote caller to access the '/mcp' endpoint and execute vault read, vault write, vault search, vault list, vault move, and vault delete operations across the entire vault. Additionally, the '/oauth/register' endpoint is unauthenticated and exposes the VAULT OAUTH CLIENT SECRET, providing a client credentials path. Proof Key for Code Exchange (PKCE), a security extension for OAuth 2.0, does not prevent this attacker-initiated flow.

Recommendations Update to version 0.2.0.