| Package | Affected versions | Patched versions |
|---|---|---|
| github.com/coder/coder | all versions | |
| github.com/coder/coder/v2 | ≥ 2.30.0, < 2.32.7≥ 2.33.0, < 2.33.8≥ 2.34.0, < 2.34.2< 2.29.17 | 2.32.72.33.82.34.22.29.17 |
| coder | ≥ 2.30.0, < 2.32.7≥ 2.33.0, < 2.33.8≥ 2.34.0, < 2.34.2< 2.29.17 | 2.32.72.33.82.34.22.29.17 |
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.
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.
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 |
Operators who cannot upgrade immediately should monitor coordinator logs for agents advertising unexpected AllowedIPs prefixes.
Coder would like to thank Anthropic's Security Team (ANT-2026-22451) for independently disclosing this issue!
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