Live Exposure Defense: From CVE to Confirmed Exposure in 12 Hours – See more

Back
New CVE Detected

CVE-2026-54618 – Unauthenticated Full Vault Access (Auth Bypass) – Obsidian Web MCP < 0.2.0

Be the first to know when new zero-days emerge:

Subscribe to Email Alerts
Subscribe to RSS Feed

Summary

CVE-2026-54618 is a critical missing-authentication vulnerability in Obsidian Web MCP, a remote Model Context Protocol (MCP) server that exposes an Obsidian vault to LLM clients such as Claude over the network. Versions prior to 0.2.0 issue a valid OAuth authorization code from the /oauth/authorize endpoint without requiring login, user consent, or a valid session, allowing that code to be exchanged for the server’s static VAULT_MCP_TOKEN. The flaw carries a CVSS v3.1 score of 9.4 (Critical) and grants a remote, unauthenticated attacker full read, write, search, list, move, and delete access to the victim’s entire Obsidian vault.

Technical details

  • Root cause: The /oauth/authorize endpoint does not perform a login, consent, or session validation check before issuing an authorization code.
  • Trigger conditions: An attacker only needs network reachability to the exposed Obsidian Web MCP instance; no valid credentials, prior session, or user interaction are required.
  • Attack vector: The attacker requests an authorization code from /oauth/authorize, then exchanges it via /oauth/token for the server’s static VAULT_MCP_TOKEN, effectively bypassing the intended OAuth 2.0 authentication flow entirely.
  • Impact: With the obtained token, the attacker can invoke MCP vault tools to read, write, search, list, move, and delete files in the connected Obsidian vault — resulting in high confidentiality and integrity impact and low availability impact (files can be moved/soft-deleted).
  • Related weaknesses identified: CWE-306 (Missing Authentication for Critical Function), CWE-522 (Insufficiently Protected Credentials), and CWE-601 (URL Redirection to Untrusted Site).

Affected software

  • obsidian-web-mcp (jimprosser) versions prior to 0.2.0

Severity

  • CVSS v3.1 Base Score: 9.4 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

Mitigation and recommended actions

  • Immediate: Upgrade obsidian-web-mcp to version 0.2.0 or later, which fixes the /oauth/authorize flow to require proper login, consent, and session validation before issuing authorization codes.
  • If unable to patch immediately:
    • Do not expose the Obsidian Web MCP server’s /oauth/authorize and /oauth/token endpoints directly to the public internet; restrict access via VPN, allow-listing, or the vendor-recommended Cloudflare Tunnel with additional access controls.
    • Rotate the VAULT_MCP_TOKEN and any credentials that may have been exposed, and audit vault contents for unauthorized reads, writes, moves, or deletions.
    • Monitor and restrict inbound network access to the MCP server until the upgrade can be applied.

References

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report

How IONIX’s External Exposure Management Platform Detects and Validates
Zero-Days to Shrink MTTR

1

Map your entire attack surface (continously)

IONIX uses multi-factor discovery methods, including DNS analysis, certificate mapping, metadata inspection, and more, to automatically map every internet-facing asset across your environment. This includes cloud instances, third-party platforms, shadow IT, and even forgotten infrastructure that traditional tools miss.

2

Monitor for new CVEs

Dozens of threat intel feeds using agentic technology are continuously analyzed to detect the appearance of proof-of-concept code, exploit kits, and indicators of active targeting. IONIX goes further by applying AI to proactively evaluate whether emerging vulnerabilities are likely to be exploited, even before PoCs go public.

3

Identify Potential External Exposures

Not all CVEs matter. IONIX filters vulnerabilities by asking attacker-centric questions: Can it be reached from the internet? Does it require authentication? Is it being exploited in the wild? This dramatically reduces noise and focuses teams on threats that can actually be weaponized.

4

Create Safe, Scalable Exploit Validations

IONIX transforms real-world PoCs into safe, non-intrusive test payloads that can be run in production environments without disruption. These simulations are precisely targeted to the systems that are vulnerable, ensuring rapid validation without unnecessary load.

5

Execute Exploit Validations

By combining context about software stack, versioning, exposure status, and reachability, IONIX ensures that only the right payloads are executed against the right assets, maximizing efficiency and minimizing risk.

6

Drive Fast and Actionable Remediation

Results are routed through integrations with ticketing, SOAR, and SIEM tools. Issues are written in plain language, bundled into remediation clusters, and prioritized based on asset criticality, exploitability, and blast radius. This shortens mean time to remediation (MTTR) and empowers teams to act with confidence.

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report
Close

Subscribe to Threat Center RSS

Copy/paste the link below into your preferred RSS reader or follow these instructions to subscribe to Slack alerts.

Open RSS feedSlack setup instructions

Close

Get Real-Time CVE Alerts to Your Email

Be the first to know when new zero-days emerge