What’s Vulnerable › Vulnerabilities

CVE-2025-59956: AgentAPI exposed user chat history via a DNS rebinding attack

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2025-09-30 · updated 2026-06-17
• Weakness: CWE-350

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.

Affected products

• coder agentapi: before 0.4.0 — fixed in 0.4.0

How to fix

Upgrade to a fixed version: coder agentapi 0.4.0. Check the vendor advisory for mitigations.

References

• https://github.blog/security/application-security/localhost-dangers-cors-and-dns-rebinding
• https://github.com/coder/agentapi/commit/5c425c62447b8a9eac19e9fc5a2eae7f0803f149
• https://github.com/coder/agentapi/pull/49
• https://github.com/coder/agentapi/releases/tag/v0.4.0
• https://github.com/coder/agentapi/security/advisories/GHSA-w64r-2g3w-w8w4
• https://mcpsec.dev/advisories/2025-09-19-coder-chat-exfiltration
• https://mcpsec.dev/advisories/2025-09-19-coder-chat-exfiltration/

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