attack vector is local; attack complexity is low; privileges required is low; user interaction is none; scope is changed; confidentiality impact is high; integrity impact is high; availability impact is none.
Affected products
canonical multipass
Classified as
CWE-22 (Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'))
Affected Products, Subsystems & Sectors
Vendor
Product
Affected Versions
Patch Status
canonical
multipass
Subsystems
General OT
Sectors
Multiple
What to Know
An issue was discovered in Canonical Multipass before version 1.16.3. The host-side SFTP server component (sshfs_server), which executes with root privileges on the host, contains a path containment bypass vulnerability within its validate_path function in src/sshfs_mount/sftp_server.cpp. The function performs a plain string prefix comparison on requested paths without path separator validation or dot-dot (..) normalization. A local attacker with root privileges inside a guest virtual machine can bypass the FUSE layer by injecting raw SFTP frames (such as an SSH_FXP_OPEN request) directly into the sshfs_server process stdin/stdout pipes via procfs. By supplying a path containing directory traversal sequences that match the allowed mount prefix, the attacker can force the host-side root process to resolve the traversal and open files outside the designated mount boundary. This allows a guest-side user to read arbitrary files on the host filesystem, resulting in a virtual machine escape. (NVD)
What to Do
Monitor canonical's web page for any future patch releases.