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TI-2026-39449 Aliases CVE-2026-54618

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

Priority HIGH 82CWE-306Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Security bypass, Information disclosure, Spoofing
Confidentiality · integrity · availability
High · High · Low
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-306, CWE-522 and CWE-601.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00507 43rd percentileScored 2026-11-07
Fix Fixed obsidian-web-mcp (jimprosser): 0.2.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
jimprosserobsidian-web-mcpbefore 0.2.00.2.0Patch availableCNA
  • obsidian-web-mcp Vendorjimprosser Affected before 0.2.0 Fixed in 0.2.0 Patch available CNA

Remediation

  • Fix · CNA obsidian-web-mcp (jimprosser) Fixed in 0.2.0

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-54618

References

Other 4

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences