An incomplete fix for a previous vulnerability left five auxiliary binaries, such as qemu-img and sshfs_server, writable by the user who installed Canonical Multipass on macOS. These binaries are invoked by the root‑privileged Multipass daemon through a PATH variable that prioritizes the user‑writable directory. A local attacker can replace one of these binaries with a malicious wrapper that the daemon will execute with root privileges, achieving privilege escalation. The weakness is reflected in CWE-276, which describes changes to the permissions of an object by a privileged process.

Canonicals Multipass for macOS, versions earlier than 1.16.3. Systems that installed the product from the default installer and did not apply the 1.16.3 update are affected. The vulnerability specifically involves binaries located in /Library/Application Support/com.canonical.multipass/bin/, including multipass, qemu-img, qemu-system-aarch64, qemu-system-x86_64, and sshfs_server.

The CVSS score of 7.8 indicates a high severity vulnerability. No EPSS score is available, but the vulnerability remains in the local threat space, requiring a user with administrative access to the machine to trigger the exploit. Since the issue is not listed in the CISA KEV catalog, there is no confirmed public exploitation yet, yet the combination of root‑level execution and user‑writable binaries makes it a serious local risk.