{"id":"UBUNTU-CVE-2026-72693","details":"`openvt -u` is intended to identify the owner of the current VT and then execute `login` as that user from a privileged context. In the documented `kbrequest`/init usage, the ownership test in `authenticate_user()` relies on `stat(\"/proc/\u003cpid\u003e/fd/0\")`. `stat()` on `/proc/\u003cpid\u003e/fd/0` follows the symlink to the underlying TTY device node. As a result, `buf.st_uid` reflects the owner of the TTY node rather than the owner of the process holding the file descriptor. If the TTY owner returns to `root` or the getty owner after logout while an unprivileged process still has `fd 0` attached to that TTY, the check can incorrectly treat that process as belonging to the privileged console owner. Once that check succeeds, the `-u` path executes a passwordless login as the selected user. In the documented `kbrequest`/init deployment using `openvt -us`, this can result in passwordless `login -f root` on the spawned VT. This report establishes that privilege escalation path for that documented deployment; it does not claim equivalent reachability for deployments that do not use `openvt -u` from a privileged `kbrequest`/init path.","modified":"2026-08-19T11:11:14Z","published":"2026-08-11T09:17:00Z","upstream":["CVE-2026-72693"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-72693"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-72693"},{"type":"REPORT","url":"https://access.redhat.com/security/cve/CVE-2026-72693"}],"affected":[{"package":{"name":"kbd","ecosystem":"Ubuntu:14.04:LTS","purl":"pkg:deb/ubuntu/kbd?arch=source&distro=trusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.15.5-1ubuntu1"],"ecosystem_specific":{"binaries":[{"binary_version":"1.15.5-1ubuntu1","binary_name":"kbd"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-72693.json"}},{"package":{"name":"kbd","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/kbd?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.15.5-1ubuntu4","1.15.5-1ubuntu5"],"ecosystem_specific":{"binaries":[{"binary_name":"kbd","binary_version":"1.15.5-1ubuntu5"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-72693.json"}},{"package":{"name":"kbd","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/kbd?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.3-2ubuntu3","2.0.4-2ubuntu1"],"ecosystem_specific":{"binaries":[{"binary_version":"2.0.4-2ubuntu1","binary_name":"kbd"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-72693.json"}},{"package":{"name":"kbd","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/kbd?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.4-4ubuntu2"],"ecosystem_specific":{"binaries":[{"binary_name":"kbd","binary_version":"2.0.4-4ubuntu2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-72693.json"}},{"package":{"name":"kbd","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/kbd?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.3.0-3ubuntu3","2.3.0-3ubuntu4","2.3.0-3ubuntu4.22.04"],"ecosystem_specific":{"binaries":[{"binary_name":"kbd","binary_version":"2.3.0-3ubuntu4.22.04"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-72693.json"}},{"package":{"name":"kbd","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/kbd?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.5.1-1ubuntu1","2.6.4-2ubuntu1","2.6.4-2ubuntu2"],"ecosystem_specific":{"binaries":[{"binary_name":"kbd","binary_version":"2.6.4-2ubuntu2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-72693.json"}},{"package":{"name":"kbd","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/kbd?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.7.1-2ubuntu1","2.7.1-2ubuntu2"],"ecosystem_specific":{"binaries":[{"binary_name":"kbd","binary_version":"2.7.1-2ubuntu2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-72693.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"},{"type":"Ubuntu","score":"medium"}]}