CVE-2026-49238 SFTP Server VM Escape in Canonical Multipass
A local attacker in a guest VM can escape to the host and read arbitrary files via a path traversal flaw in the SFTP server.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-49238?
CVE-2026-49238 is a high-severity path traversal vulnerability in Canonical Multipass, published on 28 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-22
Which versions are affected by CVE-2026-49238?
It affects 1 product.
Products include Canonical Multipass.
How do I fix CVE-2026-49238?
No fix has been published for CVE-2026-49238 yet. Limit exposure of the affected software until one is available.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-49238 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-49238 exists.
Other vulnerabilities in Canonical Multipass
Sources
Also known as GHSA-rhp2-23c4-r34w.