`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/<pid>/fd/0")`. `stat()` on `/proc/<pid>/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.
History

Tue, 11 Aug 2026 12:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Moderate


Tue, 11 Aug 2026 09:00:00 +0000

Type Values Removed Values Added
Description `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/<pid>/fd/0")`. `stat()` on `/proc/<pid>/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.
Title Kbd: local privilege escalation in openvt via incorrect process owner verification allowing passwordless root login
First Time appeared Redhat
Redhat enterprise Linux
Redhat hummingbird
Redhat openshift
Weaknesses CWE-284
CPEs cpe:/a:redhat:hummingbird:1
cpe:/a:redhat:openshift:4
cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:6
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat enterprise Linux
Redhat hummingbird
Redhat openshift
References
Metrics cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}


cve-icon MITRE

Status: PUBLISHED

Assigner: redhat

Published:

Updated: 2026-08-11T08:39:24.983Z

Reserved: 2026-08-10T12:35:16.746Z

Link: CVE-2026-72693

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-11T09:17:14.340

Modified: 2026-08-11T09:17:14.340

Link: CVE-2026-72693

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-08-11T06:58:59Z

Links: CVE-2026-72693 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-08-11T10:30:04Z