CVE-2025-59155 hackmd-mcp server-side request forgery in HTTP transport mode
Attackers can exploit SSRF in HTTP transport mode to access internal network services and bypass access controls in hackmd-mcp.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-59155?
CVE-2025-59155 is a medium-severity server-side request forgery vulnerability in yuna0x0 hackmd-mcp, published on 15 Sep 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
hackmd-mcp is a Model Context Protocol server for integrating HackMD's note-taking platform with AI assistants. From 1.4.0 to before 1.5.0, hackmd-mcp contains a server-side request forgery (SSRF) vulnerability when the server is run in HTTP transport mode. Arbitrary hackmdApiUrl values supplied via the Hackmd-Api-Url HTTP header or a base64-encoded JSON query parameter are accepted without validation, allowing attackers to redirect outbound API requests to internal network services, access internal endpoints, perform network reconnaissance, and bypass network access controls. The stdio transport mode is not affected because it only accepts stdio requests. The issue is fixed in version 1.5.0, which enforces allowed endpoints and supports the ALLOWED_HACKMD_API_URLS environment variable. Users should update to 1.5.0 or later or apply documented mitigations such as switching to stdio mode, restricting outbound network access, or filtering the Hackmd-Api-Url header and related query parameter via a reverse proxy.
Weakness: CWE-918
Which versions are affected by CVE-2025-59155?
2 open source packages ship an affected version, including hackmd-mcp.
| Package | Affected | Fixed in |
|---|---|---|
hackmd-mcp npm | From 1.4.0 | 1.5.0 |
hackmd-mcp npm | From 1.4.0 | 1.5.0 |
How do I fix CVE-2025-59155?
Upgrade hackmd-mcp to 1.5.0 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2025-59155 being exploited?
There is no known exploitation of CVE-2025-59155 in the wild and no public exploit code.
Sources
Also known as GHSA-g5cg-6c7v-mmpw.