## What Happened
Docker released a security update for critical Docker Sandboxes vulnerabilities: CVE-2026-77179 and CVE-2026-79994. The flaws allow a malicious guest to escape isolated microVM workspaces and interact with the host system. Docker states there is no confirmed exploitation yet, and patches are available in 0.42.0.
## Technical Details
- CVE-2026-77179 (CVSSv4 9.4): The macOS virtio-fs host server improperly follows symlinks when reopening unlinked files. A malicious guest can replace a parent directory with a symlink to escape the shared workspace and write arbitrary macOS host files as the VMM user.
- CVE-2026-79994 (CVSSv4 8.7): The guest-to-host Unix domain socket relay checks that a socket path is within an authorized workspace, but reconnects using the original path name. A malicious guest can exploit a time delay by replacing an intermediate directory with a symlink, forcing the host to connect to an arbitrary AF_UNIX socket outside the shared space.
## Affected
- CVE-2026-77179: macOS versions from 0.28.0 up to, but not including, 0.42.0
- CVE-2026-79994: versions from 0.37.0 up to, but not including, 0.42.0 (across platforms)
## Impact
- Guest-to-host escape from microVM isolation
- Arbitrary macOS host file writes via symlink behavior in virtio-fs
- Host Unix socket access outside the shared workspace via symlink race
## Mitigation
1. Upgrade Docker Sandboxes to 0.42.0 (Docker’s security update).
2. If upgrading is impossible, run sandboxes in clone mode.
3. Avoid adding read-write host mounts to the sandbox configuration.