CVE-2026-49238
SFTP Server VM Escape in Canonical Multipass
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.
INFO
Published Date :
May 28, 2026, 2:16 p.m.
Last Modified :
Oct. 14, 2026, 8:10 p.m.
Remotely Exploit :
No
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | cc1ad9ee-3454-478d-9317-d3e869d708bc | ||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | MITRE-CVE |
Solution
- Update Canonical Multipass to version 1.16.3 or later.
- Apply vendor patches for SSHFS server component.
- Restrict guest VM access to host resources.
- Validate all path inputs rigorously.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-49238.
| URL | Resource |
|---|---|
| https://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34w | Exploit Third Party Advisory |
| https://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34w | Exploit Third Party Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-49238 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-49238
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-49238 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-49238 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Oct. 14, 2026
Action Type Old Value New Value Added Translation Title: Multipass de Canonical, Description: Se descubrió un problema en Canonical Multipass anterior a la versión 1.16.3. El componente del servidor SFTP del lado del host (sshfs_server), que se ejecuta con privilegios de root en el host, contiene una vulnerabilidad de omisión de contención de ruta dentro de su función validate_path en src/sshfs_mount/sftp_server.cpp. La función realiza una comparación de prefijo de cadena simple en las rutas solicitadas sin validación de separador de ruta o normalización de punto-punto (..). Un atacante local con privilegios de root dentro de una máquina virtual invitada puede omitir la capa FUSE inyectando tramas SFTP sin procesar (como una solicitud SSH_FXP_OPEN) directamente en las tuberías stdin/stdout del proceso sshfs_server a través de procfs. Al proporcionar una ruta que contiene secuencias de salto de directorio que coinciden con el prefijo de montaje permitido, el atacante puede forzar al proceso root del lado del host a resolver el salto y abrir archivos fuera del límite de montaje designado. Esto permite a un usuario del lado invitado leer archivos arbitrarios en el sistema de archivos del host, lo que resulta en un escape de máquina virtual. -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'Canonical', 'product': 'Multipass', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '1.16.3', 'versionType': 'semver'}], 'defaultStatus': 'unaffected'}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-49238', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-05-28T14:23:55.283642Z'} -
Initial Analysis by [email protected]
Jun. 01, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:canonical:multipass:*:*:*:*:*:*:*:* versions up to (excluding) 1.16.3 Added Reference Type CISA-ADP: https://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34w Types: Exploit, Third Party Advisory Added Reference Type Canonical Ltd.: https://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34w Types: Exploit, Third Party Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
May. 28, 2026
Action Type Old Value New Value Added Reference https://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34w -
New CVE Received by [email protected]
May. 28, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N Added CWE CWE-22 Added Reference https://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34w