GHSA-wrq8-fcv5-8hvp: Coder: Route hijacking through lack of validation of agent-supplied AllowedIPs in tailnet coordinator
Coder's tailnet coordinator component fails to validate agent-supplied AllowedIPs against the authenticating agent's UUID, allowing a malicious authenticated agent to advertise arbitrary IP prefixes. This can lead to route hijacking where the malicious agent intercepts traffic intended for other agents by claiming their tailnet IP addresses. The vulnerability requires an authenticated user with a running workspace and a modified agent binary. Official patches have been released to validate AllowedIPs properly.
AI Analysis
Technical Summary
The tailnet coordinator in Coder validates that an agent's Addresses correspond to its authenticated UUID but does not apply the same validation to AllowedIPs. As a result, a malicious workspace agent can advertise arbitrary AllowedIPs prefixes, including those belonging to other agents. Since routing is based on tailnet IPs, this enables the malicious agent to intercept and spoof traffic destined for other agents. Exploitation requires an authenticated user with a running workspace and a modified agent binary. The issue is fixed by validating AllowedIPs prefixes against the authenticating agent's UUID, with patches backported to all supported release lines.
Potential Impact
A malicious authenticated agent can hijack network routes by advertising IP prefixes assigned to other agents, allowing interception and spoofing of web terminal and workspace application traffic. This compromises confidentiality and integrity of communications within the tailnet. The vulnerability does not affect availability. Exploitation requires authentication and a modified agent binary, limiting the attack surface to insiders or compromised users.
Mitigation Recommendations
Official patches are available and have been backported to all supported release lines: 2.34.2, 2.33.8, 2.32.7, and 2.29.17. Operators should upgrade to these versions to remediate the vulnerability. For those unable to upgrade immediately, monitoring coordinator logs for agents advertising unexpected AllowedIPs prefixes is recommended as a temporary mitigation.
GHSA-wrq8-fcv5-8hvp: Coder: Route hijacking through lack of validation of agent-supplied AllowedIPs in tailnet coordinator
Description
Coder's tailnet coordinator component fails to validate agent-supplied AllowedIPs against the authenticating agent's UUID, allowing a malicious authenticated agent to advertise arbitrary IP prefixes. This can lead to route hijacking where the malicious agent intercepts traffic intended for other agents by claiming their tailnet IP addresses. The vulnerability requires an authenticated user with a running workspace and a modified agent binary. Official patches have been released to validate AllowedIPs properly.
CVSS v3.1
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The tailnet coordinator in Coder validates that an agent's Addresses correspond to its authenticated UUID but does not apply the same validation to AllowedIPs. As a result, a malicious workspace agent can advertise arbitrary AllowedIPs prefixes, including those belonging to other agents. Since routing is based on tailnet IPs, this enables the malicious agent to intercept and spoof traffic destined for other agents. Exploitation requires an authenticated user with a running workspace and a modified agent binary. The issue is fixed by validating AllowedIPs prefixes against the authenticating agent's UUID, with patches backported to all supported release lines.
Potential Impact
A malicious authenticated agent can hijack network routes by advertising IP prefixes assigned to other agents, allowing interception and spoofing of web terminal and workspace application traffic. This compromises confidentiality and integrity of communications within the tailnet. The vulnerability does not affect availability. Exploitation requires authentication and a modified agent binary, limiting the attack surface to insiders or compromised users.
Mitigation Recommendations
Official patches are available and have been backported to all supported release lines: 2.34.2, 2.33.8, 2.32.7, and 2.29.17. Operators should upgrade to these versions to remediate the vulnerability. For those unable to upgrade immediately, monitoring coordinator logs for agents advertising unexpected AllowedIPs prefixes is recommended as a temporary mitigation.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-wrq8-fcv5-8hvp
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-55428"]
- Ecosystems
- ["Go"]
- Database Specific Severity
- HIGH
- Cvss Version
- 3.1
Threat ID: 6a4c340327e9c797195f5f45
Added to database: 07/06/2026, 23:02:27 UTC
Last enriched: 07/06/2026, 23:12:46 UTC
Last updated: 07/06/2026, 23:12:46 UTC
Views: 2
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