CVE-2026-90043 zram: fix slot lock bit position on big-endian 64-bit
A race condition in the Linux kernel zram driver on big-endian systems allows concurrent slot access, potentially causing denial of service or data corruption.
- 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-2026-90043?
CVE-2026-90043 is a high-severity vulnerability in Linux, published on 16 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 slot lock bit position on big-endian 64-bit
The slot lock is a bit operation on the whole __lock word, which flags and ac_time alias as two u32s. On little-endian the lock bit lands in the position ZRAM_ENTRY_LOCK reserves in flags, so the aliasing works out. On 64-bit big-endian it lands in ac_time instead: with ZRAM_TRACK_ENTRY_ACTIME enabled, storing the access time from mark_slot_accessed() or slot_free() wipes out the held lock bit, letting another CPU take the same slot lock; an access time value with that bit set makes the slot look locked forever.
Shift the lock bit into the flags half of the word on big-endian 64-bit.
Which versions are affected by CVE-2026-90043?
How do I fix CVE-2026-90043?
Apply the vendor's patch.
Is CVE-2026-90043 being exploited?
There is no known exploitation of CVE-2026-90043 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-90043, GHSA-6w7g-56x2-f4jj, UBUNTU-CVE-2026-90043.