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GHSA-g5cg-6c7v-mmpw — hackmd-mcp

Fix: yuna0x0/hackmd-mcp@43936c7

GHSA-g5cg-6c7v-mmpw is a Server-Side Request Forgery (SSRF) vulnerability in hackmd-mcp. A fix is available for hackmd-mcp — see the affected versions and patch details below.

HackMD MCP Server has Server-Side Request Forgery (SSRF) vulnerability

Also known asCVE-2025-59155
Published
Sep 15, 2025
Updated
Sep 15, 2025
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Sep 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-g5cg-6c7v-mmpw.

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs29th percentile — riskier than 29% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

0other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
hackmd-mcpnpm
87downloads / week

Description

Impact

A Server-Side Request Forgery (SSRF) vulnerability that affects all users running the HackMD MCP server in HTTP mode. Attackers could exploit this vulnerability by passing arbitrary hackmdApiUrl values through HTTP headers (Hackmd-Api-Url) or base64-encoded JSON query parameters. This allows malicious users to:

  • Redirect API calls to internal network services
  • Potentially access sensitive internal endpoints
  • Perform network reconnaissance through the server
  • Bypass network access controls

The vulnerability affects the HTTP transport mode specifically - stdio mode is not impacted as it only accepts requests from stdio.

Patches

The vulnerability has been patched in version 1.5.0. Users should:

  1. Update to the latest version of the HackMD MCP server
  2. Set the ALLOWED_HACKMD_API_URLS environment variable to restrict allowed HackMD API endpoints
  3. If not set, the server will default to only allowing the official HackMD API URL (https://api.hackmd.io/v1)

Example configuration:

ALLOWED_HACKMD_API_URLS=https://api.hackmd.io/v1,https://your-hackmd-instance.com/api/v1

Workarounds

Users can mitigate this vulnerability without upgrading by:

  1. Use stdio mode instead of HTTP mode: Set TRANSPORT=stdio or remove the TRANSPORT environment variable to disable HTTP mode entirely
  2. Network-level restrictions: Use firewall rules or network policies to restrict outbound connections from the server
  3. Reverse proxy filtering: Place the MCP server behind a reverse proxy that validates and filters both the Hackmd-Api-Url header and the base64-encoded JSON config query parameter to prevent malicious hackmdApiUrl values

References

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmhackmd-mcp≥ 1.4.0&&< 1.5.01.5.0npm install hackmd-mcp@1.5.0

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hackmd-mcp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update hackmd-mcp to 1.5.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-g5cg-6c7v-mmpw is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-g5cg-6c7v-mmpw can be triaged on real exposure rather than presence alone.

Tailored to GHSA-g5cg-6c7v-mmpw. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Impact A Server-Side Request Forgery (SSRF) vulnerability that affects all users running the HackMD MCP server in HTTP mode. Attackers could exploit this vulnerability by passing arbitrary `hackmdApiUrl` values through HTTP headers (`Hackmd-Api-Url`) or base64-encoded JSON query parameters. This allows malicious users to: - Redirect API calls to internal network services - Potentially access sensitive internal endpoints - Perform network reconnaissance through the server - Bypass network access controls The vulnerability affects the HTTP transport mode specifically - stdio mode is not i
O3 Security · Impact-Aware SCA

Is GHSA-g5cg-6c7v-mmpw in your dependencies?

O3 Security finds GHSA-g5cg-6c7v-mmpw across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

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GHSA-g5cg-6c7v-mmpw: hackmd-mcp SSRF | O3 Security