FKIE_CVE-2026-49238

Vulnerability from fkie_nvd - Published: 2026-05-28 14:16 - Updated: 2026-06-01 13:26
Severity
8.4 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
Summary
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.
References
security@ubuntu.comhttps://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34wThird Party Advisory, Exploit
134c704f-9b21-4f2e-91b3-4a467353bcc0https://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34wThird Party Advisory, Exploit
Impacted products
Vendor Product Version
canonical multipass *
To clipboard 

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:canonical:multipass:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "633AA429-4296-43D2-8F9F-D5115F121BD3",
              "versionEndExcluding": "1.16.3",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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."
    }
  ],
  "id": "CVE-2026-49238",
  "lastModified": "2026-06-01T13:26:31.580",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "NONE",
          "baseScore": 8.4,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "CHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.0,
        "impactScore": 5.8,
        "source": "security@ubuntu.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-05-28T14:16:24.403",
  "references": [
    {
      "source": "security@ubuntu.com",
      "tags": [
        "Third Party Advisory",
        "Exploit"
      ],
      "url": "https://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34w"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "tags": [
        "Third Party Advisory",
        "Exploit"
      ],
      "url": "https://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34w"
    }
  ],
  "sourceIdentifier": "security@ubuntu.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-22"
        }
      ],
      "source": "security@ubuntu.com",
      "type": "Secondary"
    }
  ]
}


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