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CVE-2026-49238— SFTP Server VM Escape in Canonical Multipass

CVSS 8.4 · High
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I. Basic Information for CVE-2026-49238

Vulnerability Information
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Vulnerability Title
SFTP Server VM Escape in Canonical Multipass
Source: NVD (National Vulnerability Database)
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.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
对路径名的限制不恰当(路径遍历)
Source: NVD (National Vulnerability Database)

Affected Products

VendorProductAffected VersionsCPESubscribe
CanonicalMultipass 0 ~ 1.16.3 -

II. Public POCs for CVE-2026-49238

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III. Intelligence Information for CVE-2026-49238

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Vendor Advisories for CVE-2026-49238 (1)

Same Patch Batch · Canonical · 2026-05-28 · 14 CVEs total

CVE-2026-492377.8 HIGHLocal Privilege Escalation in Canonical Multipass
CVE-2026-473317.8 HIGHUse-after-free in Ubuntu Linux AppArmor notification handling
CVE-2026-473337.8 HIGHOut-of-bounds read in Ubuntu Linux AppArmor notification handling
CVE-2026-473286.1 MEDIUMInvalid pointer deallocation in Ubuntu Linux AppArmor notification handling
CVE-2026-473325.5 MEDIUMOut-of-bounds read in Ubuntu Linux AppArmor notification handling
CVE-2026-473345.5 MEDIUMDeadlock or kernel panic in Ubuntu Linux AppArmor notification handling
CVE-2026-473265.5 MEDIUMMemory leak in Ubuntu Linux AppArmor large notification response allocation
CVE-2026-473355.5 MEDIUMNULL pointer dereference in Ubuntu Linux AppArmor notification handling
CVE-2026-473363.3 LOWUse of uninitialized value in Ubuntu Linux AppArmor IPv4/IPv6 socket mediation rules
CVE-2026-473273.3 LOWNULL pointer dereference in Ubuntu Linux AppArmor notification handling
CVE-2026-473373.3 LOWNULL pointer dereference in Ubuntu Linux AppArmor IPv4/IPv6 socket mediation
CVE-2026-473303.3 LOWUse of uninitialized value in Ubuntu Linux AppArmor notification handling
CVE-2026-473293.3 LOWIncorrect validation of field size in Ubuntu Linux AppArmor notification responses

IV. Related Vulnerabilities

Same product: Multipass
Same vendor: Canonical
Same weakness: CWE-22

V. Comments for CVE-2026-49238

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