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Fencer Intel
medium 6.5

CVE-2025-59956 json

AgentAPI exposed user chat history via a DNS rebinding attack

published last yr. modified 4mo ago also GHSA-w64r-2g3w-w8w4 , GO-2025-3991 , EUVD-2025-31619

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 37%
public exploits
0
none known

Summary

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.

Patch / fix

  • go github.com/coder/agentapi 0.4.0
  • coder agentapi 0.4.0
  • govulncheck-vulndb SLE Module for Package Hub 15 SP6, openSUSE Leap 15.6 0.0.20251023T162509-150000.1.110.1

suse advisories SUSE-SU-2025:3799-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
  • govulncheck-vulndb openSUSE Tumbleweed 0.0.20251023T162509-1.1

opensuse advisories openSUSE-SU-2026:21483-1openSUSE-SU-2025:15666-1

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
last yr.

Exploit prediction

0.43% chance of exploitation in the next 30 days, higher than 37% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • mcpsec.dev https://mcpsec.dev/advisories/2025-09-19-coder-chat-exfiltration/ referenced PoC, tagged "exploit" by a source, unverified
  • mcpsec.dev https://mcpsec.dev/advisories/2025-09-19-coder-chat-exfiltration referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
GitHub 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
go github.com/coder/agentapi
<0.4.0
0.4.0

Affected products

  • coder agentapi

Classification

Weakness
  • CWE-350 Reliance on Reverse DNS Resolution for a Security-Critical Action
  • CWE-290 Authentication Bypass by Spoofing

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.