CVE-2026-55428
highpriority · track · 0OT risk · elevatedEPSS 0.004 · 35 %ileEUUSEPSS · scored 2026-10-27
Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, 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. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 validates each `AllowedIPs` prefix against the authenticating agent's UUID just like `Addresses`. As a workaround, monitor coordinator logs for agents advertising unexpected `AllowedIPs` prefixes.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
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affected products (13)
Products and version ranges known to be affected.
advisories (2)
Vendor and ecosystem advisories describing this.
- GHSA-wrq8-fcv5-8hvpCoder: Route hijacking through lack of validation of agent-supplied AllowedIPs in tailnet coordinator2026-07-06ghsa · osvUS
### 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](https://github.com/coder/coder/releases/tag/v2.34.2) | | 2.33 | [v2.33.8](https://github.com/coder/coder/releases/tag/v2.33.8) | | 2.32 | [v2.32.7](https://github.com/coder/coder/releases/tag/v2.32.7) | | 2.29 (ESR) | [v2.29.17](https://github.com/coder/coder/releases/tag/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!
- GO-2026-5915Coder: Route hijacking through lack of validation of agent-supplied AllowedIPs in tailnet coordinator in github.com/coder/coder2026-07-07vendor · osvUS
Coder: Route hijacking through lack of validation of agent-supplied AllowedIPs in tailnet coordinator in github.com/coder/coder
also known as (5)
Other names and identifiers for this entity.
sources
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references (19)
External citations — patches, advisories, analysis.
- https://github.com/coder/coder/pull/26144cnnvd
- https://github.com/coder/coder/releasesPatchcnnvd
- https://github.com/coder/coder/releases/tag/v2.29.17cnnvd
- https://github.com/coder/coder/releases/tag/v2.32.7cnnvd
- https://github.com/coder/coder/releases/tag/v2.33.8cnnvd
- https://github.com/coder/coder/releases/tag/v2.34.2cnnvd
- https://github.com/coder/coder/security/advisories/GHSA-wrq8-fcv5-8hvpcnnvd
- https://github.com/coder/coder/pull/26144enisa_euvd
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