CVE-2026-53402

What the bug is

When fbcon_do_set_font() fails (e.g., due to a memory allocation failure inside vc_resize() under heavy memory pressure), it jumps to the `err_out` label to roll back the console state. However, the current rollback logic forgets to restore the `hi_font` state, leading to a severe state machine corruption. Earlier in the function, `set_vc_hi_font()` might be called to change `vc->vc_hi_font_mask` and mutate the screen buffer. If `vc_resize()` subsequently fails, the `err_out` path restores `vc_font.charcount` but entirely skips rolling back the `vc_hi_font_mask` and the screen buffer. This mismatch leaves the terminal in a desynchronized state. Because `vc_hi_font_mask` remains set, the VT subsystem will still accept character indices greater than 255 from userspace and write them to the screen buffer. Subsequent rendering calls (e.g., `fbcon_putcs()`) will then use these inflated indices to access the reverted, 256-character font array, leading to a deterministic out-of-bounds read and potential kernel memory disclosure. Fix this by adding the missing rollback logic for the `hi_font` mask and screen buffer in the error path.

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

drivers/video/fbdev/core/fbcon.c

What this is

FRAMEBUFFER CONSOLEMAINTAINERS section matched on drivers/video/fbdev/core/fbcon.c · dri-devel@lists.freedesktop.org · Maintained

Check it on the machine

grep -wE 'CONFIG_FB|CONFIG_FB_CORE|CONFIG_FRAMEBUFFER_CONSOLE' /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

Show whether Debian builds this, per release

Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.

• bookwormy
• trixie, forky, sidYnot built on s390x/s390x
• bookworm · linux-6.12y

y

built into the kernel image on every flavour - only a patch removes it

Y

built in where it is built at all; some flavours do not build it

Build switches

CONFIG_FB, CONFIG_FB_CORE, CONFIG_FRAMEBUFFER_CONSOLE

Reads as

all on means the file is compiled; any one off means it is not.

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-07-19 (3 months ago)source

CVSS

7.1 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:Hsource recompute it

Attack vector

local (AV:L)source

EPSS

0.14%, higher than 2.7% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

drivers/video

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
5.10.249	5.10.261	cb016bcb40c8
5.15.64	5.15.212	ac562193c366
6.0	6.1.178	3618a4c5b259
6.0	6.6.145	a7a526fbc847
6.0	6.12.96	b5bb2c696e14
6.0	6.18.39	076b1aa65f77
6.0	7.1.3	39815715cbcf
6.0	7.2	8fdc8c2057ee
5.19.6	0	0

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