CVE-2026-89718 zram: fix out-of-bounds access in writeback_store()
A race condition in the Linux kernel zram module allows local attackers to trigger out-of-bounds memory access, potentially leading to code execution or privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89718?
CVE-2026-89718 is a vulnerability in Linux, published on 11 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:
zram: fix out-of-bounds access in writeback_store()
Patch series "zram: fix stale scan bounds after reinitialization".
Both writeback_store() and read_block_state() derive their table scan bounds from zram->disksize before acquiring dev_lock. If the device is reset and reinitialized with a smaller disksize between that read and lock acquisition, the bound can describe the old table while the scan operates on the new one. This can lead to out-of-bounds slot accesses.
Move both bound calculations under dev_lock so each bound remains consistent with the table throughout its scan. Keep the fixes separate because the affected interfaces originate from different commits and can be backported independently.
This patch (of 2):
writeback_store() calculates the table scan bounds before taking dev_lock. A reset followed by reconfiguration with a smaller disksize can therefore replace zram->table while writeback_store() is waiting for the lock. Once it acquires the lock, it sees an initialized device but scans the new table using the old upper bound, resulting in an out-of-bounds access.
Calculate the number of pages while holding dev_lock so the scan bound matches the table protected by the lock.
Which versions are affected by CVE-2026-89718?
How do I fix CVE-2026-89718?
Apply the vendor's patch.
Is CVE-2026-89718 being exploited?
There is no known exploitation of CVE-2026-89718 in the wild and no public exploit code.
Sources
Also known as AZL-100151, BELL-CVE-2026-89718, DEBIAN-CVE-2026-89718, GHSA-8g3j-f4r3-9992, UBUNTU-CVE-2026-89718.