Canonical Multipass up to 1.16.2 Host-side SFTP Server sftp_server.cpp path traversal

Summaryinfo

A vulnerability was found in Canonical Multipass up to 1.16.2 and classified as critical. Affected by this vulnerability is an unknown functionality of the file src/sshfs_mount/sftp_server.cpp of the component Host-side SFTP Server. The manipulation results in path traversal. This vulnerability is reported as CVE-2026-49238. The attack requires a local approach. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, was found in Canonical Multipass up to 1.16.2. Affected is an unknown code of the file src/sshfs_mount/sftp_server.cpp of the component Host-side SFTP Server. The manipulation with an unknown input leads to a path traversal vulnerability. CWE is classifying the issue as CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-49238 since 05/28/2026. The exploitability is told to be easy. Local access is required to approach this attack. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1006 by the MITRE ATT&CK project.

Upgrading to version 1.16.3 eliminates this vulnerability.

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Productinfo

Vendor

• Canonical

Name

• Multipass

Version

• 1.16.0
• 1.16.1
• 1.16.2

License

• open-source

Website

• Product: https://github.com/canonical/multipass/

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CPE 2.2info

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