In BuildKit versions older than 0.34.1 a malicious client with access to the control APIs can supply a build request that writes an extended attribute to a file outside the expected BuildKit state directory. The extended attribute names may belong to the trusted. or security. namespace, which, if set, can grant a program running on the host elevated privileges. This flaw allows the attacker to manipulate file attributes on the host filesystem, bypassing normal ownership and permission checks.

Vulnerable systems include Moby BuildKit deployments using any version earlier than 0.34.1. The affected component is the BuildKit service that relies on the control API to coordinate build steps.

The CVSS score of 4.5 indicates a moderate impact. No EPSS data exists, and the vulnerability is not listed in CISA’s KEV catalog, suggesting limited publicly known exploitation. The likely attack vector is a remote client that can contact the BuildKit control API, which may be exposed over HTTP or gRPC. If an attacker can send a crafted build request, they may set privileged extended attributes, potentially causing privilege escalation or compromising host integrity. Current mitigations involve applying the vendor patch and restricting API access to trusted clients.