CVE-2026-49238— Canonical Multipass 安全漏洞

SFTP Server VM Escape in Canonical Multipass

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:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

对路径名的限制不恰当(路径遍历)

Canonical Multipass 安全漏洞

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

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