What is CVE-2025-59956?

CVE-2025-59956 is a medium-severity vulnerability in Coder Agentapi, classified under CWE-350. CVSS score: 6.5/10. Published 2025-09-30.

How severe is CVE-2025-59956?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Is CVE-2025-59956 known to be exploited?

2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Coder Agentapi

CVE-2025-59956

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.

Published 2025-09-30 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.004 (35.4th percentile), scored 2026-10-19.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 35th percentile — 35.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

Coder Agentapi — versions < 0.4.0

Weakness classification (CWE)

Public proof-of-concept exploits

References

github.com/coder/agentapi/security/advisories/GHSA-w64r-2g3w-w8w4 (Patch, Vendor Advisory)
github.com/coder/agentapi/pull/49 (Patch, Issue Tracking)
github.com/coder/agentapi/commit/5c425c62447b8a9eac19e9fc5a2eae7f0803f149 (Patch)
github.blog/security/application-security/localhost-dangers-cors-and-dns-rebind… (Technical Description)
github.com/coder/agentapi/releases/tag/v0.4.0 (Release Notes)
mcpsec.dev/advisories/2025-09-19-coder-chat-exfiltration (Exploit, Third Party Advisory)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2025-59956?: CVE-2025-59956 is a medium-severity vulnerability in Coder Agentapi, classified under CWE-350. CVSS score: 6.5/10. Published 2025-09-30.
How severe is CVE-2025-59956?: Medium severity. CVSS v3 base score is 6.5 out of 10.
Is CVE-2025-59956 known to be exploited?: 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.