Vulnerability Description
AgentAPI is an HTTP API for Claude Code, Goose, Aider, Gemini, Amp, and Codex. Versions 0.3.3 and below are susceptible to a client-side DNS rebinding attack when hosted over plain HTTP on localhost. An attacker can gain access to the /messages endpoint served by the Agent API. This allows for the unauthorized exfiltration of sensitive user data, specifically local message history, which can include secret keys, file system contents, and intellectual property the user was working on locally. This issue is fixed in version 0.4.0.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Coder | Agentapi | < 0.4.0 |
Related Weaknesses (CWE)
References
- https://github.blog/security/application-security/localhost-dangers-cors-and-dnsTechnical Description
- https://github.com/coder/agentapi/commit/5c425c62447b8a9eac19e9fc5a2eae7f0803f14Patch
- https://github.com/coder/agentapi/pull/49Issue TrackingPatch
- https://github.com/coder/agentapi/releases/tag/v0.4.0Release Notes
- https://github.com/coder/agentapi/security/advisories/GHSA-w64r-2g3w-w8w4PatchVendor Advisory
- https://mcpsec.dev/advisories/2025-09-19-coder-chat-exfiltrationExploitThird Party Advisory
- https://mcpsec.dev/advisories/2025-09-19-coder-chat-exfiltration/ExploitThird Party Advisory
FAQ
What is CVE-2025-59956?
CVE-2025-59956 is a vulnerability with a CVSS score of 6.5 (MEDIUM). AgentAPI is an HTTP API for Claude Code, Goose, Aider, Gemini, Amp, and Codex. Versions 0.3.3 and below are susceptible to a client-side DNS rebinding attack when hosted over plain HTTP on localhost. ...
How severe is CVE-2025-59956?
CVE-2025-59956 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2025-59956?
Check the references section above for vendor advisories and patch information. Affected products include: Coder Agentapi.