Vulnerability Description
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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Canonical | Multipass | < 1.16.3 |
Related Weaknesses (CWE)
References
- https://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34wExploitThird Party Advisory
- https://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34wExploitThird Party Advisory
FAQ
What is CVE-2026-49238?
CVE-2026-49238 is a vulnerability with a CVSS score of 8.4 (HIGH). 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 b...
How severe is CVE-2026-49238?
CVE-2026-49238 has been rated HIGH with a CVSS base score of 8.4/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-49238?
Check the references section above for vendor advisories and patch information. Affected products include: Canonical Multipass.