CVE-2026-49237: Local Privilege Escalation in Canonical Multipass

Synopsis

A local privilege escalation vulnerability affects Canonical Multipass for macOS before version 1.16.3. An attacker who already has a low-privilege shell on the host can replace one of five user-writable auxiliary binaries (such as qemu-img) in a directory that the root LaunchDaemon searches first when resolving bare binary names; when the daemon later invokes that binary during normal operation, the attacker's code runs with root privileges. Successful exploitation gives the attacker full read, write, and execution access as root on the affected system. A patched-image rebuild at version 1.16.3 is available on HarborGuard for environments running an affected version.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityNot required

  The attacker needs an existing shell or process on the host; no network access to the service is required to exploit this vulnerability.

• AuthenticationRequired

  Any low-privilege local account is sufficient; the attacker does not need administrative or root credentials to stage the malicious binary replacement.

• Victim interactionNot required

  No user interaction is needed; the exploit triggers automatically when the root LaunchDaemon invokes the replaced binary during routine daemon execution.

• Attack complexityDetail

  The exploit is reliable and condition-free: writing a replacement binary to the user-writable directory is a straightforward file operation with no race conditions or special memory layout requirements.

Blast Radius

• The attacker gains code execution as root, reading any file on the system including credentials, private keys, and application secrets.
• The attacker can write or modify any file on the system, including system binaries, configuration files, and persistent storage.
• The attacker can terminate or manipulate any running process, including security agents and logging daemons.
• Full root access allows the attacker to install persistent backdoors or kernel extensions that survive reboots.