CVE-2026-43497 fbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free
A use-after-free in the udlfb driver allows local attackers to execute code or escalate privileges via stale memory mappings after USB disconnect.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-43497?
CVE-2026-43497 is a high-severity use after free vulnerability in Linux kernel, published on 21 May 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
In the Linux kernel, the following vulnerability has been resolved:
fbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free
dlfb_ops_mmap() uses remap_pfn_range() to map vmalloc framebuffer pages to userspace but sets no vm_ops on the VMA. This means the kernel cannot track active mmaps. When dlfb_realloc_framebuffer() replaces the backing buffer via FBIOPUT_VSCREENINFO, existing mmap PTEs are not invalidated. On USB disconnect, dlfb_ops_destroy() calls vfree() on the old pages while userspace PTEs still reference them, resulting in a use-after-free: the process retains read/write access to freed kernel pages.
Add vm_operations_struct with open/close callbacks that maintain an atomic mmap_count on struct dlfb_data. In dlfb_realloc_framebuffer(), check mmap_count and return -EBUSY if the buffer is currently mapped, preventing buffer replacement while userspace holds stale PTEs.
Tested with PoC using dummy_hcd + raw_gadget USB device emulation.
Weakness: CWE-416
Which versions are affected by CVE-2026-43497?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43497?
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-2026-43497 being exploited?
There is no known exploitation of CVE-2026-43497 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-87071, BELL-CVE-2026-43497, DEBIAN-CVE-2026-43497, GHSA-233x-r9gj-mfg9, ROOT-OS-DEBIAN-11-CVE-2026-43497, ROOT-OS-DEBIAN-12-CVE-2026-43497 and 3 more.