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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Red Hat | Red Hat Enterprise Linux 10 | — | — |
| Red Hat | Red Hat Enterprise Linux 8 | — | — |
| Red Hat | Red Hat Enterprise Linux 9 | — | — |
| Red Hat | Red Hat OpenShift Container Platform 4.22 | — | — |
| Red Hat | Red Hat Hardened Images | — | — |
| Red Hat | Red Hat Enterprise Linux 6 | — | — |
| Red Hat | Red Hat Enterprise Linux 7 | — | — |
| Red Hat | Red Hat OpenShift Container Platform 4 | — | — |
| Red Hat | Red Hat OpenShift Container Platform 5 | — | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | kbd | 2.10.0-1 | — |
| Debian 13 | kbd | No fix yet | — |
| Debian 12 | kbd | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | kbd | No fix yet | — |
| Ubuntu 26.04 LTS | kbd | No fix yet | — |
| Ubuntu 24.04 LTS | kbd | No fix yet | — |
| Ubuntu 22.04 LTS | kbd | No fix yet | — |
| Ubuntu 20.04 LTS | kbd | No fix yet | — |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | kbd | No fix yet | — |
| Ubuntu 16.04 LTS | kbd | No fix yet | — |
| Ubuntu 14.04 LTS | kbd | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 10 | kbd +2 | 2.6.4-8.el10_2 | RHSA-2026:57597 |
| RHEL 9 | kbd +2 | 2.4.0-12.el9_8 | RHSA-2026:57610 |
| RHEL 8 | kbd +2 | 2.0.4-11.el8_10.1 | RHSA-2026:78951 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Hardened Images 1 | kbd +2 | 2.10.0-2.hum1 | RHSA-2026:41136 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 10 | kbd +2 | 2.6.4-8.el10_2 | ALSA-2026:57597 |
| AlmaLinux 9 | kbd +2 | 2.4.0-12.el9_8 | ALSA-2026:57610 |
| AlmaLinux 8 | kbd +2 | 2.0.4-11.el8_10.1 | ALSA-2026:78951 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 10 | kbd | 2.6.4-8.el10_2 | RLSA-2026:57597 |
| Rocky Linux 9 | kbd | 2.4.0-12.el9_8 | RLSA-2026:57610 |
| Rocky Linux 8 | kbd | 2.0.4-11.el8_10.1 | RLSA-2026:78951 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | kbd | 2.4.0-150700.15.10.1 | SUSE-SU-2026:4211-1 |
| SLES 15 SP6 | kbd | 2.4.0-150400.5.12.1 | SUSE-SU-2026:4207-1 |
| SLES 15 SP5 | kbd | 2.4.0-150400.5.12.1 | SUSE-SU-2026:4207-1 |
| SLES 15 SP4 | kbd | 2.4.0-150400.5.12.1 | SUSE-SU-2026:4207-1 |
Show 13 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | kbd | 2.7.1-160000.3.1 | SUSE-SU-2026:23911-1 |
| SLES for SAP 15 SP6 | kbd | 2.4.0-150400.5.12.1 | SUSE-SU-2026:4207-1 |
| SLES for SAP 15 SP5 | kbd | 2.4.0-150400.5.12.1 | SUSE-SU-2026:4207-1 |
| SLES for SAP 15 SP4 | kbd | 2.4.0-150400.5.12.1 | SUSE-SU-2026:4207-1 |
| SLES 16.0 | kbd | 2.7.1-160000.3.1 | SUSE-SU-2026:23911-1 |
| SLE Micro 6.2 | kbd | 2.7.1-160000.3.1 | SUSE-SU-2026:23893-1 |
| SLE Micro 6.1 | kbd | 2.6.4-slfo.1.1_2.1 | SUSE-SU-2026:23742-1 |
| SLE Micro 6.0 | kbd | 2.6.4-2.1 | SUSE-SU-2026:23844-1 |
| SLE Micro 5.5 | kbd | 2.4.0-150400.5.12.1 | SUSE-SU-2026:4207-1 |
| SLE Micro 5.4 | kbd | 2.4.0-150400.5.12.1 | SUSE-SU-2026:4207-1 |
| SLE Micro 5.3 | kbd | 2.4.0-150400.5.12.1 | SUSE-SU-2026:4207-1 |
| SLE HPC 15 SP5 | kbd | 2.4.0-150400.5.12.1 | SUSE-SU-2026:4207-1 |
| SLE HPC 15 SP4 | kbd | 2.4.0-150400.5.12.1 | SUSE-SU-2026:4207-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 16.0 | kbd | 2.7.1-160000.3.1 | openSUSE-SU-2026:21939-1 |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | kbd +2 | 2.4.0-2.amzn2023.0.4 | ALAS2023-2026-2109 |
| Amazon Linux 2 | kbd +2 | 1.15.5-15.amzn2.0.1 | ALAS2-2026-3885 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | kbd | 2.2.0-3 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 10 | kbd +2 | 2.6.4-8.el10_2 | ELSA-2026-57597 |
| Oracle Linux 9 | kbd +2 | 2.4.0-12.el9_8 | ELSA-2026-57610 |
| Oracle Linux 8 | kbd +2 | 2.0.4-11.el8_10.1 | ELSA-2026-78951 |
Advisories 23
- WID-SEC-2026-2961 Red Hat Enterprise Linux (mrtg, kbd, urwid): Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 3, 2026
- ALSA-2026:57610 Moderate: kbd security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2026:57597 Moderate: kbd security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2026:78951 Moderate: kbd security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2026:78951 Red Hat Security Advisory: kbd security update Red Hat Security Advisories (RHSA) · Oct 10, 2026
- RHSA-2026:57610 Red Hat Security Advisory: kbd security update Red Hat Security Advisories (RHSA) · Oct 10, 2026
- RHSA-2026:57597 Red Hat Security Advisory: kbd security update Red Hat Security Advisories (RHSA) · Oct 10, 2026
- RHSA-2026:41136 Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update Red Hat Security Advisories (RHSA) · Oct 10, 2026
- RLSA-2026:78951 Moderate: kbd security update Rocky Linux Security Advisories · Oct 9, 2026
- ELSA-2026-78951 Moderate: kbd security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Oct 8, 2026
- SUSE-SU-2026:23911-1 Security update for kbd SUSE / openSUSE Security Updates · Sep 30, 2026
- SUSE-SU-2026:23893-1 Security update for kbd SUSE / openSUSE Security Updates · Sep 30, 2026
- SUSE-SU-2026:23844-1 Security update for kbd SUSE / openSUSE Security Updates · Sep 27, 2026
- SUSE-SU-2026:23742-1 Security update for kbd SUSE / openSUSE Security Updates · Sep 27, 2026
- openSUSE-SU-2026:21939-1 Security update for kbd SUSE / openSUSE Security Updates · Sep 25, 2026
- SUSE-SU-2026:4207-1 Security update for kbd SUSE / openSUSE Security Updates · Sep 16, 2026
- SUSE-SU-2026:4211-1 Security update for kbd SUSE / openSUSE Security Updates · Sep 16, 2026
- ALAS2-2026-3885 Important: kbd security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Aug 31, 2026
- ALAS2023-2026-2109 Important: kbd security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Aug 31, 2026
- RLSA-2026:57597 Moderate: kbd security update Rocky Linux Security Advisories · Aug 21, 2026
- RLSA-2026:57610 Moderate: kbd security update Rocky Linux Security Advisories · Aug 21, 2026
- ELSA-2026-57597 Moderate: kbd security update (Oracle Linux 10) Oracle Linux Security Advisories (ELSA) · Aug 20, 2026
- ELSA-2026-57610 Moderate: kbd security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Aug 20, 2026
References
- RHSA-2026:41136 vendor-advisory
- RHSA-2026:57597 vendor-advisory
- RHSA-2026:57610 vendor-advisory
- RHSA-2026:60440 vendor-advisory
- RHSA-2026:66357 vendor-advisory
- RHSA-2026:78951 vendor-advisory
- https://access.redhat.com/security/cve/CVE-2026-72693 vdb-entry
- RHBZ#2462115 issue-tracking