PT-2026-44376 · Canonical · Multipass
Published
2026-05-28
·
Updated
2026-05-28
·
CVE-2026-49238
CVSS v3.1
8.4
High
| Vector | AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N |
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.
Exploit
Fix
Path traversal
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Weakness Enumeration
Related Identifiers
Affected Products
Multipass