CVE-2026-53403

What the bug is

info->var, a framebuffer's current mode, is expected to have a matching entry in info->modelist. var_to_display() relies on this and treats a failed fb_match_mode() as "This should not happen". fb_set_var() keeps it true by adding the mode to the list on every change, and do_register_framebuffer() does the same at registration. store_modes() replaces the modelist from userspace. fb_new_modelist() validates the new modes but does not check that info->var still has a match. It relies on fbcon_new_modelist() to re-point consoles, but that only handles consoles mapped to the framebuffer. With fbcon unbound there are none, so info->var is left describing a mode that is no longer in the list. A later console takeover runs var_to_display(), where fb_match_mode() returns NULL and leaves fb_display[i].mode NULL. fbcon_switch() passes it to display_to_var(), and fb_videomode_to_var() dereferences the NULL mode. Keep the current mode in the list in fb_new_modelist(), the same way fb_set_var() does.

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/fbmem.c

What this is

FRAMEBUFFER COREMAINTAINERS section matched on drivers/video/fbdev/core/ · Odd Fixes

Check it on the machine

grep -wE 'CONFIG_FB|CONFIG_FB_CORE' /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

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

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

no vector published, unrated

Attack vector

not published

EPSS

0.13%, higher than 2.3% 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
2.6.12	5.10.260	1458a4d80455
2.6.12	5.15.211	8707f02ac9f5
2.6.12	6.1.177	0d8c7f21ad85
2.6.12	6.6.144	7640b4f68acb
2.6.12	6.12.95	4f1a7fe8ba84
2.6.12	6.18.38	eea16b6f805c
2.6.12	7.1.3	88913059c77e
2.6.12	7.2	7f08fc10fa3d

Debian advisories