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

Quick assessment

Affected
Canonical Multipass
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Canonical Multipass是Canonical开源的一个Ubuntu的虚拟实例。 Canonical Multipass 1.16.3之前版本存在安全漏洞，该漏洞源于sshfs_server组件中validate_path函数存在路径包含绕过问题，仅执行字符串前缀比较而未进行路径分隔符验证或..规范化，可能导致具有root权限的本地攻击者通过procfs向sshfs_server进程stdin/stdout管道注入原始SFTP帧，强制主机端root进程解析遍历并打开指定挂载边界之外的文件，导致

CVSS 8.4 · High EPSS 0.45% · P36

Affected Version Matrix 1

VendorProduct Version RangeStatus
Canonical Multipass < 1.16.3 affected
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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: CVE Program / CVE List V5
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: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对路径名的限制不恰当(路径遍历)
Source: CVE Program / CVE List V5
Vulnerability Title
Canonical Multipass 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Canonical Multipass是Canonical开源的一个Ubuntu的虚拟实例。 Canonical Multipass 1.16.3之前版本存在安全漏洞，该漏洞源于sshfs_server组件中validate_path函数存在路径包含绕过问题，仅执行字符串前缀比较而未进行路径分隔符验证或..规范化，可能导致具有root权限的本地攻击者通过procfs向sshfs_server进程stdin/stdout管道注入原始SFTP帧，强制主机端root进程解析遍历并打开指定挂载边界之外的文件，导致
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Canonical Multipass 0 ~ 1.16.3 -

II. Public POCs for CVE-2026-49238

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 10582 chars
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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-2026-49237 7.8 HIGH Local Privilege Escalation in Canonical Multipass
CVE-2026-47331 7.8 HIGH Use-after-free in Ubuntu Linux AppArmor notification handling
CVE-2026-47333 7.8 HIGH Out-of-bounds read in Ubuntu Linux AppArmor notification handling
CVE-2026-47328 6.1 MEDIUM Invalid pointer deallocation in Ubuntu Linux AppArmor notification handling
CVE-2026-47332 5.5 MEDIUM Out-of-bounds read in Ubuntu Linux AppArmor notification handling
CVE-2026-47334 5.5 MEDIUM Deadlock or kernel panic in Ubuntu Linux AppArmor notification handling
CVE-2026-47326 5.5 MEDIUM Memory leak in Ubuntu Linux AppArmor large notification response allocation
CVE-2026-47335 5.5 MEDIUM NULL pointer dereference in Ubuntu Linux AppArmor notification handling
CVE-2026-47336 3.3 LOW Use of uninitialized value in Ubuntu Linux AppArmor IPv4/IPv6 socket mediation rules
CVE-2026-47327 3.3 LOW NULL pointer dereference in Ubuntu Linux AppArmor notification handling
CVE-2026-47337 3.3 LOW NULL pointer dereference in Ubuntu Linux AppArmor IPv4/IPv6 socket mediation
CVE-2026-47330 3.3 LOW Use of uninitialized value in Ubuntu Linux AppArmor notification handling
CVE-2026-47329 3.3 LOW Incorrect 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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