VulnerabilityPublished 29 Sep 2025

CVE-2025-59956: coder agentapi · Reliance on Reverse DNS Resolution for a Security-Critical Action

Affects coder agentapiSource CVE Database V5

Not known to be exploited · CVSS 6.5 Medium : upgrade to 0.4.0 when convenient.

Data as of 26 Oct 2026, 12:55 UTC

CVSS 3.1 base score

6.5Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 36% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.4.0

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 29 Sep 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade coder agentapi to 0.4.0.

Affected software

Product	Affected	Fixed in
coder agentapi	Affected <0.4.0	Fixed in 0.4.0

AI-suggested

Upgrade all AgentAPI deployments to version 0.4.0 or later immediately to apply the official fix.
Enforce HTTPS for all localhost API communications to prevent interception and manipulation of DNS responses.
Disable reliance on reverse DNS resolution for security decisions within the API or implement strict validation of DNS responses.
Implement strict origin and referer header checks to ensure requests to the /messages endpoint originate from trusted sources.
Restrict access to the AgentAPI localhost endpoints using firewall rules or local network policies to prevent unauthorized external access.
Educate users about the risks of visiting untrusted websites that could trigger DNS rebinding attacks.
Monitor network traffic for suspicious DNS rebinding patterns or unexpected localhost API requests.
Consider implementing authentication and authorization mechanisms on localhost APIs to prevent unauthorized access.
Conduct regular security audits and penetration testing focused on localhost API exposures and DNS-related attack vectors.

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.

Impact

For European organizations, especially those involved in software development, AI-assisted coding, or using coder's AgentAPI, this vulnerability poses a significant risk of sensitive data leakage. The unauthorized access to local message history can expose secret keys, proprietary code, and intellectual property, potentially leading to intellectual property theft, loss of competitive advantage, and compliance violations under GDPR due to unauthorized data exposure. Attackers can exploit this remotely with minimal complexity, requiring only that a user visits a malicious website. This risk is amplified in environments where developers use AgentAPI on their local machines without HTTPS or proper access controls. The confidentiality impact is high, but integrity and availability remain unaffected. The vulnerability could also facilitate further attacks if secret keys or credentials are exfiltrated. Organizations with remote or hybrid work models may be more vulnerable due to increased exposure to phishing or malicious websites. The lack of authentication on the API endpoint and reliance on insecure HTTP further exacerbate the threat.

CWE-350Reliance on Reverse DNS Resolution for a Security-Critical Action (opens in a new tab)
Variant weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
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.
Architecture and Design
Use other means of identity verification that cannot be simply spoofed. Possibilities include a username/password or certificate.
Implementation
Perform proper forward and reverse DNS lookups to detect DNS spoofing.
OWASP Cheat Sheets
Docker Security (opens in a new tab)
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V10.3.3 (opens in a new tab)
V2.8.5 (opens in a new tab)
V2.8.4 (opens in a new tab)
Attack patterns
DNS Cache Poisoning (opens in a new tab)
DNS Rebinding (opens in a new tab)
User-Controlled Filename (opens in a new tab)
Pharming (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 7 Oct 2025, 00:51 UTC

WeaknessesCWE-350

Technical details

References

Community reviews

Related threats