CVE-2026-53403 fbdev: Fix fb_new_modelist to prevent null-ptr-deref in fb_videomode_to_var
A null pointer dereference in the Linux kernel framebuffer driver allows local attackers to cause a system crash via console takeover.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53403?
CVE-2026-53403 is a medium-severity vulnerability in Linux kernel, published on 19 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
fbdev: Fix fb_new_modelist to prevent null-ptr-deref in fb_videomode_to_var
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.
Weakness: CWE-476
Which versions are affected by CVE-2026-53403?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53403?
Apply the vendor's patch.
Is CVE-2026-53403 being exploited?
There is no known exploitation of CVE-2026-53403 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-92549, BELL-CVE-2026-53403, DEBIAN-CVE-2026-53403, GHSA-mppp-59pm-fqxw, ROOT-OS-UBUNTU-2204-CVE-2026-53403, UBUNTU-CVE-2026-53403.