CVE-2026-80785 fbdev: serialize mode sysfs access with lock_fb_info()
A use-after-free vulnerability in the Linux kernel's fbdev subsystem allows local attackers to execute arbitrary code or escalate privileges via concurrent sysfs access.
- 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-2026-80785?
CVE-2026-80785 is an use after free vulnerability in Linux, published on 4 Sep 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: serialize mode sysfs access with lock_fb_info()
show_mode(), show_modes(), and store_mode() access fb_info->modelist and fb_info->mode without holding lock_fb_info(). store_modes() takes lock_fb_info() while replacing the modelist and freeing the old one.
A concurrent reader or writer can load a pointer to an old modelist entry before store_modes() frees it, then dereference freed memory or store a stale freed pointer in fb_info->mode.
Take lock_fb_info() in show_mode(), show_modes(), and store_mode() to serialize with store_modes(). In show_mode(), copy the mode to the stack and format after dropping the lock. In store_mode(), split activate() into a _locked variant to avoid double-locking, and hold the locks for the modelist walk, mode conversion, activation, and fb_info->mode assignment together.
Which versions are affected by CVE-2026-80785?
How do I fix CVE-2026-80785?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-80785 being exploited?
There is no known exploitation of CVE-2026-80785 in the wild and no public exploit code.
Sources
Also known as AZL-99434, BELL-CVE-2026-80785, DEBIAN-CVE-2026-80785, GHSA-9wwr-625v-fr4h, UBUNTU-CVE-2026-80785.