AgentAPI exposed user chat history via a DNS rebinding attack
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.
Impact Analysis
Refer to official advisory for detailed impact metrics.
Remediation
Ensure systems are updated to the latest vendor-supplied patch levels.
Am I Vulnerable?
Launch our assessment wizard to check if your infrastructure is exposed to • CVE-2025-59956
Credits & Attribution
No credits recorded in the NVD database.
References
- https://github.com/coder/agentapi/security/advisories/GHSA-w64r-2g3w-w8w4
- https://github.com/coder/agentapi/pull/49
- https://github.com/coder/agentapi/commit/5c425c62447b8a9eac19e9fc5a2eae7f0803f149
- https://github.blog/security/application-security/localhost-dangers-cors-and-dns-rebinding
- https://github.com/coder/agentapi/releases/tag/v0.4.0
- https://mcpsec.dev/advisories/2025-09-19-coder-chat-exfiltration
More from coder
View All →Affected Vendor
coder
View all reports →Affected Software
Timeline
CVSS Vectors
Weaknesses (CWE)
MITRE ATT&CK TTPs
No associated TTPs found for this vulnerability.