Atlantis mistakenly concatenates user‑controlled workspace names into filesystem paths without proper validation. The result is that an attacker can craft a request with traversal segments—such as "../../"—to cause the application to create or delete arbitrary directories on the host. Because these operations run with the same privileges as the Atlantis process, the attacker can either erase critical data or create files that will be used in subsequent Terraform runs, resulting in integrity loss or denial of service.

The affected versions are runatlantis:atlantis 0.19.8 through 0.45.0. The product is a self‑hosted Golang application that receives Terraform pull‑request webhook events. Any deployment of these versions that allows authenticated access to the /api/plan endpoint or accepts repository‑level workspace definitions is vulnerable.

With a CVSS score of 8.1, this vulnerability carries a high potential for exploitation. The EPSS score is not disclosed, and the issue is not currently listed in the CISA KEV catalog, but the lack of path validation and the local‑privilege requirement mean that any attacker capable of influencing the workspace value can trigger destructive filesystem actions. The attack vector is likely to be an authenticated API call or an adversary who can modify the atlantis.yaml file for a repository that the application processes.