The tailnet coordinator in Coder validates an agent's Addresses against its authenticated UUID but neglects to perform the same validation on the AllowedIPs list supplied by the agent. Because the coordinator forwards the agent-supplied AllowedIPs verbatim into the WireGuard configuration of tunnel peers, a malicious or compromised agent can inject arbitrary IP prefixes into the network. This enables route hijacking and unauthorized routing of traffic, representing a serious authority bypass flaw (CWE-285) and parameter tampering (CWE-863).

The vulnerability is present in Coder deployments using the tailnet coordinator when agent registrations are accepted without proper AllowedIPs validation, specifically affecting versions older than 2.29.7, 2.32.7, 2.33.8, and 2.34.2. Organizations using Terraform to provision remote development environments through these earlier releases are at risk.

With a CVSS score of 8.2 the issue poses a high severity risk to confidentiality, integrity, and availability. The EPSS score of < 1% indicates a very low exploitation probability, and the vulnerability is not listed in CISA’s KEV catalog. The likely attack vector requires an agent that can authenticate to the coordinator; once authenticated, the attacker can supply malicious AllowedIPs prefixes, a process that appears straightforward due to the missing validation. Successful exploitation would allow the attacker to hijack network routes and potentially divert or intercept traffic to and from the affected development environments.