Espreto

An issue was discovered in Canonical Multipass for macOS before version 1.16.3 due to an incomplete fix for CVE-2025-5199. While the patch in version 1.16.0 updated the ownership of the multipassd daemon binary to root:wheel, five co-located binaries (multipass, qemu-img, qemu-system-aarch64, qemu-system-x86 64, and sshfs server) in /Library/Application Support/com.canonical.multipass/bin/ retain ownership by the installing user and remain writable. Because the root LaunchDaemon (com.canonical.multipassd.plist) configures a PATH environment variable that prioritizes this user-writable directory and invokes these auxiliary binaries by their bare names, a local attacker can replace an auxiliary binary (such as qemu-img) with a malicious wrapper. When the root daemon subsequently triggers the binary during routine execution (e.g., via multipass launch), the malicious code executes with root privileges, leading to local privilege escalation.

**Name of the Vulnerable Software and Affected Versions** Canonical Multipass versions prior to 1.16.3 **Description** The host-side SFTP server component (sshfs server), which runs with root privileges on the host, contains a path containment bypass in the `validate path()` function located in src/sshfs mount/sftp server.cpp. The function uses a plain string prefix comparison for requested paths but fails to perform path separator validation or dot-dot (..) normalization. A local attacker with root privileges inside a guest virtual machine can bypass the FUSE (Filesystem in Userspace) layer—a mechanism that allows non-privileged users to create their own file systems—by injecting raw SFTP frames, such as an SSH FXP OPEN request, directly into the sshfs server process stdin/stdout pipes via procfs. By using directory traversal sequences that match the allowed mount prefix, the attacker can force the host-side root process to open files outside the designated mount boundary, enabling the reading of arbitrary files on the host filesystem and resulting in a virtual machine escape. **Recommendations** Update to version 1.16.3 or later.