kernel: vt: skip screen update for DEC alignment test on backgroup consoles (CVE-2026-98838)

Overview

A flaw was found in the Linux kernel's virtual terminal subsystem. When handling screen updates for background consoles, the kernel fails to properly verify that a console is active before redrawing it with modified font dimensions. A local attacker can exploit this issue by altering font settings and issuing control sequences to an inactive console, triggering an out-of-bounds memory read against an unresized buffer. This can lead to a system crash, resulting in a Denial of Service (DoS), or potentially expose sensitive kernel memory.

Vendor advisories

• Red Hat VEX · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, … · updated 2026-10-23 · vex

kernel: vt: skip screen update for DEC alignment test on backgroup consoles — rated Moderate by Red Hat. Released 2026-10-18, updated 2026-10-23.

Affected:

• Red Hat Enterprise Linux 10
• Red Hat Enterprise Linux 7
• Red Hat Enterprise Linux 8
• Red Hat Enterprise Linux 9
• Red Hat OpenShift Container Platform 4

No fix planned:

• Red Hat Enterprise Linux 10
• Red Hat Enterprise Linux 7
• Red Hat Enterprise Linux 8
• Red Hat Enterprise Linux 9
• Red Hat OpenShift Container Platform 4

Not affected:

• Red Hat Enterprise Linux 6

Remediation

Fix deferred