Executive brief
Docker Sandboxes is a feature that allows running isolated guest environments on a host system. The guest-to-host Unix socket relay, which enables controlled communication between the sandboxed guest and the host, contains a path-validation vulnerability. An attacker with guest access can exploit a time-of-check-time-of-use (TOCTOU) flaw by replacing intermediate directories with symlinks after validation, allowing arbitrary socket connections outside the authorized workspace and potentially exposing sensitive host data or capabilities.
Technical details
The vulnerability is a time-of-check-time-of-use (TOCTOU) flaw in the guest-to-host Unix-domain socket relay. The vulnerable component validates that a socket path resides within an authorized workspace, but then uses the original pathname to establish the connection without re-validating. A malicious guest can replace an intermediate directory component with a symlink between the validation step and the actual connection, causing the host to connect to an arbitrary AF_UNIX socket outside the shared workspace. This allows exposure of data or host-side capabilities bound to targeted sockets. The vulnerability requires guest-level access to trigger, and the attack is path-based rather than network-based. A patch should implement atomic path resolution or re-validation at connection time.
Affected products
- Docker Sandboxes
Timeline
- 2026-09-15: disclosed