CVE-2025-59956: coder agentapi
Vulnerability summary
CVE-2025-59956 is a medium (CVSS 6.5) vulnerability in coder agentapi. EPSS estimates a 0.43% chance of exploitation in the next 30 days, higher than 35.3% of scored vulnerabilities. 2 public exploits are recorded.
Advisory lineage
Upstream 0 · Downstream 3 · Related 3Timeline
- 29-09-2025PublishedVulnerability first disclosed.
- 30-09-2025Last modifiedVulnerability information updated.
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 metrics
3 scores · 3 sources · 1 version- OSV · GoEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
- NVDNIST6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
EPSS trend
Probability
0.43%
Chance of exploitation in the next 30 days
Percentile
35%
Versus all other CVEs
30-day change
0.00 pp
From 0.43% on 18-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
2 foundExploit Reference (mcpsec.dev)
Maturity: unknown
Exploit Reference (mcpsec.dev)
Maturity: unknown
Weaknesses
CWE · root cause- CWE-350Reliance on Reverse DNS Resolution for a Security-Critical ActionThe product performs reverse DNS resolution on an IP address to obtain the hostname and make a security decision, but it does not properly ensure that the IP address is truly associated with the hostname.
- CWE-290Authentication Bypass by SpoofingThis attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.
Affected systems
Coder1 product
- agentapi< 0.4.0
Github.com/coder1 product
- agentapi< 0.4.0
2 vendors · 2 products
References
10 links- github.com/coder/agentapi/security/advisories/GHSA-w64r-2g3w-w8w4X Refsource CONFIRMWEBAdvisoryPatchVendor Advisory
- github.com/coder/agentapi/commit/5c425c62447b8a9eac19e9fc5a2eae7f0803f149X Refsource MISCWEBFIXPatch
- github.blog/security/application-security/localhost-dangers-cors-and-dns-rebindingX Refsource MISCWEBTechnical Description
- mcpsec.dev/advisories/2025-09-19-coder-chat-exfiltrationX Refsource MISCWEBExploitThird Party Advisory
- github.com/coder/agentapiPACKAGE