CVE-2026-80859 fuse: fix missing barrier when checking io-uring readiness
A missing memory barrier in the Linux kernel FUSE module can cause a race condition leading to a deadlock and denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80859?
CVE-2026-80859 is a 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:
fuse: fix missing barrier when checking io-uring readiness
fuse_block_alloc() reads fch->initialized and then fch->io_uring. fch->io_uring is set before fch->initialized, ordered by the smp_wmb() in fuse_chan_set_intialized(), but fuse_block_alloc() has no matching read barrier between the two loads.
This may lead a CPU to observe fch->initialized=1 but fch->io_uring=0, and skip the check that blocks request allocation until the io-uring queues are ready. This can reintroduce the lock-order inversion deadlock that commit 3393ff964e0f prevents.
Add an smp_rmb() barrier to pair with the smp_wmb() in fuse_chan_set_initialized() to prevent this.
Which versions are affected by CVE-2026-80859?
How do I fix CVE-2026-80859?
Apply the vendor's patch.
Is CVE-2026-80859 being exploited?
There is no known exploitation of CVE-2026-80859 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-80859, DEBIAN-CVE-2026-80859, GHSA-66f3-f7p7-8q9g, UBUNTU-CVE-2026-80859.