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.
Problem types
CWE-350: Reliance on Reverse DNS Resolution for a Security-Critical Action
Product status
References
github.com/...entapi/security/advisories/GHSA-w64r-2g3w-w8w4
github.com/coder/agentapi/pull/49
github.com/...ommit/5c425c62447b8a9eac19e9fc5a2eae7f0803f149
github.blog/...rity/localhost-dangers-cors-and-dns-rebinding
github.com/coder/agentapi/releases/tag/v0.4.0
mcpsec.dev/advisories/2025-09-19-coder-chat-exfiltration
