CVE-2025-59956: Github.com/coder/agentapi Coder AgentAPI Exposed User Chat Vulnerability
MODERATECVE-2025-59956 is a MODERATE (CVSS 6.5) coder agentapi exposed user chat vulnerability (CWE-350: Reliance on Reverse DNS Resolution for a Security-Critical Action) affecting Github.com/coder/agentapi libraries in the Go ecosystem. The issue involves coder agentapi exposed user chat history via a dns rebinding attack. Remediation is available by upgrading affected packages to version 0.4.0.
CVE-2025-59956 at a Glance
Security Impact
CVSS: 6.5
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N).
How to Fix CVE-2025-59956
To remediate this vulnerability, upgrade all affected Github.com/coder/agentapi dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade github.com/coder/agentapi to 0.4.0Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for github.com/coder/agentapiHow to Check if You Are Affected
To determine whether your application is affected by CVE-2025-59956, inspect your project dependencies for Github.com/coder/agentapi:
inspect dependencies for github.com/coder/agentapiAnalyze the terminal output to locate any version of Github.com/coder/agentapi in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.4.0), your application is affected.
Note: Verify declared build manifests and deployed runtime container environments.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-350: Reliance on Reverse DNS Resolution for a Security-Critical Action, where the 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. In Github.com/coder/agentapi, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2025-59956 Affected Github.com/coder/agentapi Versions
1 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
github.com/coder/agentapi
|
Go |
< 0.4.0
|
0.4.0
|
References
Frequently Asked Questions
What is CVE-2025-59956?
Which Github.com/coder/agentapi versions are affected?
What version fixes CVE-2025-59956?
Is github.com/coder/agentapi affected?
What is the CVSS score of CVE-2025-59956?
What CWE is associated with CVE-2025-59956?
How can I check Go dependencies for CVE-2025-59956?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-w64r-2g3w-w8w4",
"modified" : "2025-10-23T20:33:23Z",
"published" : "2025-09-29T20:40:26Z",
"aliases" : [ "CVE-2025-59956" ],
"summary" : "Coder AgentAPI exposed user chat history via a DNS rebinding attack",
"details" : "### Summary\nAgentAPI prior to version [0.4.0](https://github.com/coder/agentapi/releases/tag/v0.4.0) was susceptible to a client-side DNS rebinding attack when hosted over plain HTTP on localhost.\n\n### Impact\nAn attacker could have gained access to the `/messages` endpoint served by the Agent API. This allowed for the unauthorized exfiltration of sensitive user data, specifically local message history, which could've included secret keys, file system contents, and intellectual property the user was working on locally.\n\n### Remediation\nWe've [implemented](https://github.com/coder/agentapi/pull/49) an `Origin` and `Host` header validating middleware and set a secure by default configuration.\n\nPlease upgrade to version [0.4.0](https://github.com/coder/agentapi/releases/tag/v0.4.0) or later.\n\n### Credits\nWe'd like to thank [Evan Harris](https://github.com/eharris128) from [mcpsec.dev](https://mcpsec.dev/) for reporting this issue and following the coordinated disclosure [policy](https://coder.com/security/policy).",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/coder/agentapi"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "0.4.0"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/coder/agentapi/security/advisories/GHSA-w64r-2g3w-w8w4"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2025-59956"
}, {
"type" : "WEB",
"url" : "https://github.com/coder/agentapi/pull/49"
}, {
"type" : "WEB",
"url" : "https://github.com/coder/agentapi/commit/5c425c62447b8a9eac19e9fc5a2eae7f0803f149"
}, {
"type" : "WEB",
"url" : "https://github.blog/security/application-security/localhost-dangers-cors-and-dns-rebinding"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/coder/agentapi"
}, {
"type" : "WEB",
"url" : "https://github.com/coder/agentapi/releases/tag/v0.4.0"
}, {
"type" : "WEB",
"url" : "https://mcpsec.dev/advisories/2025-09-19-coder-chat-exfiltration"
}, {
"type" : "WEB",
"url" : "https://pkg.go.dev/vuln/GO-2025-3991"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-290", "CWE-350" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2025-09-29T20:40:26Z",
"nvd_published_at" : "2025-09-30T11:37:41Z"
}
}