CVE-2026-54618 Obsidian Web MCP: Unauthenticated vault access: /oauth/authorize auto-approves without authenticating the user
Unauthenticated attackers can bypass OAuth checks to read, write, and delete files in Obsidian vaults via the Web MCP server.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-54618?
CVE-2026-54618 is a critical authentication bypass vulnerability in jimprosser obsidian-web-mcp, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Obsidian Web MCP is a secure remote MCP server for Obsidian vaults. Prior to 0.2.0, /oauth/authorize issues an authorization code without a login, consent, or session check, and /oauth/token can exchange that code for the static VAULT_MCP_TOKEN without authenticating a client. An unauthenticated remote caller who can reach the intended tunnel deployment can therefore call /mcp and use vault_read, vault_write, vault_search, vault_list, vault_move, and vault_delete against the entire vault. Optional PKCE does not prevent an attacker-initiated flow, and unauthenticated /oauth/register also exposes a client_credentials path by returning the configured VAULT_OAUTH_CLIENT_SECRET. This issue is fixed in version 0.2.0.
Which versions are affected by CVE-2026-54618?
How do I fix CVE-2026-54618?
No fix has been published for CVE-2026-54618 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-54618 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-54618 exists.
Sources
Also known as GHSA-hwhg-mrjc-8g43.