What is GHSA-wrq8-fcv5-8hvp?

GHSA-wrq8-fcv5-8hvp is a security advisory published by GitHub Security Advisories with High severity. Coder: Route hijacking through lack of validation of agent-supplied AllowedIPs in tailnet coordinator

Which CVE IDs does GHSA-wrq8-fcv5-8hvp cover?

GHSA-wrq8-fcv5-8hvp covers the following CVE IDs: CVE-2026-55428. Each CVE has its own detail page on EchelonGraph Pulse with the synthesized EG score.

What is the CVSS v3 score of GHSA-wrq8-fcv5-8hvp?

GHSA-wrq8-fcv5-8hvp has a CVSS v3 base score of 8.2, published by GitHub Security Advisories.

Which products are affected by GHSA-wrq8-fcv5-8hvp?

GHSA-wrq8-fcv5-8hvp affects 4 products, including: go/github.com/coder/coder/v2:\u003e= 2.34.0, \u003c 2.34.2; go/github.com/coder/coder/v2:\u003e= 2.33.0, \u003c 2.33.8; go/github.com/coder/coder/v2:\u003e= 2.30.0, \u003c 2.32.7; go/github.com/coder/coder/v2:\u003c 2.29.17.

GHSA-wrq8-fcv5-8hvpHighCVSS 8.2

Coder: Route hijacking through lack of validation of agent-supplied AllowedIPs in tailnet coordinator

Vendor

GitHub Security Advisories

Published

July 6, 2026

Last Modified

July 6, 2026

🔗 CVE IDs covered (1)

CVE-2026-55428 →

📋 Description

Summary

The tailnet coordinator validates that an agent's Addresses derive from its authenticated UUID but applies no equivalent check to AllowedIPs. The coordinator forwards agent-supplied AllowedIPs verbatim to tunnel peers which install them into the WireGuard peer configuration.

Impact

A malicious workspace agent can advertise arbitrary AllowedIPs prefixes including another agent's tailnet address. Coder's ServerTailnet routes to agents by tailnet IP so an agent that claims a victim's prefix can intercept web terminal and workspace app traffic and serve spoofed content. Exploitation requires an authenticated user with a running workspace and a modified agent binary.

Patches

The fix validates each AllowedIPs prefix against the authenticating agent's UUID just like Addresses.

The fix was backported to all supported release lines:

| Release line | Patched version | |---|---| | 2.34 | v2.34.2 | | 2.33 | v2.33.8 | | 2.32 | v2.32.7 | | 2.29 (ESR) | v2.29.17 |

Workarounds

Operators who cannot upgrade immediately should monitor coordinator logs for agents advertising unexpected AllowedIPs prefixes.

Resources

Fix: #26144

Credits

Coder would like to thank Anthropic's Security Team (ANT-2026-22451) for independently disclosing this issue!

🎯 Affected products4

go/github.com/coder/coder/v2:>= 2.34.0, < 2.34.2
go/github.com/coder/coder/v2:>= 2.33.0, < 2.33.8
go/github.com/coder/coder/v2:>= 2.30.0, < 2.32.7
go/github.com/coder/coder/v2:< 2.29.17