Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-05-01T00:00:00 kernel: vt: discard stale unicode buffer on alt screen exit after resize 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CWE-131

In the Linux kernel, the following vulnerability has been resolved: vt: discard stale unicode buffer on alt screen exit after resize When enter_alt_screen() saves vc_uni_lines into vc_saved_uni_lines and sets vc_uni_lines to NULL, a subsequent console resize via vc_do_resize() skips reallocating the unicode buffer because vc_uni_lines is NULL. However, vc_saved_uni_lines still points to the old buffer allocated for the original dimensions. When leave_alt_screen() later restores vc_saved_uni_lines, the buffer dimensions no longer match vc_rows/vc_cols. Any operation that iterates over the unicode buffer using the current dimensions (e.g. csi_J clearing the screen) will access memory out of bounds, causing a kernel oops: BUG: unable to handle page fault for address: 0x0000002000000020 RIP: 0010:csi_J+0x133/0x2d0 The faulting address 0x0000002000000020 is two adjacent u32 space characters (0x20) interpreted as a pointer, read from the row data area past the end of the 25-entry pointer array in a buffer allocated for 80x25 but accessed with 240x67 dimensions. Fix this by checking whether the console dimensions changed while in the alternate screen. If they did, free the stale saved buffer instead of restoring it. The unicode screen will be lazily rebuilt via vc_uniscr_check() when next needed.

A flaw was found in the Linux kernel. When a console is resized while in an alternate screen mode, the system may fail to properly update its internal buffer for unicode characters. This can lead to an out-of-bounds memory access when the alternate screen mode is exited, potentially causing a system crash (kernel oops) and resulting in a Denial of Service (DoS).

The console/vt layer could retain a stale unicode buffer across alt-screen resize transitions; upstream discards it safely. Red Hat treats this as local TTY memory hygiene. Patch kernels; vt is core. Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Fix deferred kernel Red Hat Enterprise Linux 7 Fix deferred kernel-rt Red Hat Enterprise Linux 8 Fix deferred kernel Red Hat Enterprise Linux 8 Fix deferred kernel-rt Red Hat Enterprise Linux 9 Fix deferred kernel Red Hat Enterprise Linux 9 Fix deferred kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-31742 https://nvd.nist.gov/vuln/detail/CVE-2026-31742 https://lore.kernel.org/linux-cve-announce/2026050140-CVE-2026-31742-e1b4@gregkh/T