CVE-2023-53826 ubi: Fix UAF wear-leveling entry in eraseblk_count_seq_show()
A use-after-free vulnerability in the Linux kernel UBI subsystem allows local attackers to potentially execute code or escalate privileges via race conditions in wear-leveling entry handling.
- 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-2023-53826?
CVE-2023-53826 is an use after free vulnerability in Linux, published on 9 Dec 2025. 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:
ubi: Fix UAF wear-leveling entry in eraseblk_count_seq_show()
Wear-leveling entry could be freed in error path, which may be accessed again in eraseblk_count_seq_show(), for example:
__erase_worker eraseblk_count_seq_show wl = ubi->lookuptbl[*block_number] if (wl) wl_entry_destroy ubi->lookuptbl[e->pnum] = NULL kmem_cache_free(ubi_wl_entry_slab, e) erase_count = wl->ec // UAF!
Wear-leveling entry updating/accessing in ubi->lookuptbl should be protected by ubi->wl_lock, fix it by adding ubi->wl_lock to serialize wl entry accessing between wl_entry_destroy() and eraseblk_count_seq_show().
Fetch a reproducer in [Link].
Which versions are affected by CVE-2023-53826?
How do I fix CVE-2023-53826?
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-2023-53826 being exploited?
There is no known exploitation of CVE-2023-53826 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2023-53826, DEBIAN-CVE-2023-53826, GHSA-39w7-pr2v-3x67, UBUNTU-CVE-2023-53826.