CVE-2026-49238

{"id": "CVE-2026-49238", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"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"}}], "cvssMetricV31": [{"type": "Secondary", "source": "security@ubuntu.com", "cvssData": {"scope": "CHANGED", "version": "3.1", "baseScore": 8.4, "attackVector": "LOCAL", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "NONE", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH"}, "impactScore": 5.8, "exploitabilityScore": 2.0}]}, "affected": [{"source": "security@ubuntu.com", "affectedData": [{"vendor": "Canonical", "product": "Multipass", "versions": [{"status": "affected", "version": "0", "lessThan": "1.16.3", "versionType": "semver"}], "defaultStatus": "unaffected"}]}], "published": "2026-05-28T14:16:24.403", "references": [{"url": "https://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34w", "tags": ["Exploit", "Third Party Advisory"], "source": "security@ubuntu.com"}, {"url": "https://github.com/canonical/multipass/security/advisories/GHSA-rhp2-23c4-r34w", "tags": ["Exploit", "Third Party Advisory"], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "security@ubuntu.com", "description": [{"lang": "en", "value": "CWE-22"}]}], "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."}, {"lang": "es", "value": "Se descubri\u00f3 un problema en Canonical Multipass anterior a la versi\u00f3n 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 omisi\u00f3n de contenci\u00f3n de ruta dentro de su funci\u00f3n validate_path en src/sshfs_mount/sftp_server.cpp. La funci\u00f3n realiza una comparaci\u00f3n de prefijo de cadena simple en las rutas solicitadas sin validaci\u00f3n de separador de ruta o normalizaci\u00f3n de punto-punto (..). Un atacante local con privilegios de root dentro de una m\u00e1quina virtual invitada puede omitir la capa FUSE inyectando tramas SFTP sin procesar (como una solicitud SSH_FXP_OPEN) directamente en las tuber\u00edas stdin/stdout del proceso sshfs_server a trav\u00e9s 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 l\u00edmite 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 m\u00e1quina virtual."}], "lastModified": "2026-10-14T20:10:00.190", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:canonical:multipass:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "633AA429-4296-43D2-8F9F-D5115F121BD3", "versionEndExcluding": "1.16.3"}], "operator": "OR"}]}], "sourceIdentifier": "security@ubuntu.com"}