CVE-2026-23168 flex_proportions: make fprop_new_period() hardirq safe

Medium 5.5 Published 14 Feb 2026 Updated 11 May 2026

A race condition in the Linux kernel's flexible proportions code can cause an infinite loop and system hang when specific block device configurations are used.

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-2026-23168?

CVE-2026-23168 is a medium-severity vulnerability in Linux kernel, published on 14 Feb 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:

flex_proportions: make fprop_new_period() hardirq safe

Bernd has reported a lockdep splat from flexible proportions code that is essentially complaining about the following race:

<timer fires> run_timer_softirq - we are in softirq context call_timer_fn writeout_period fprop_new_period write_seqcount_begin(&p->sequence);

<hardirq is raised> ... blk_mq_end_request() blk_update_request() ext4_end_bio() folio_end_writeback() __wb_writeout_add() __fprop_add_percpu_max() if (unlikely(max_frac < FPROP_FRAC_BASE)) { fprop_fraction_percpu() seq = read_seqcount_begin(&p->sequence); - sees odd sequence so loops indefinitely

Note that a deadlock like this is only possible if the bdi has configured maximum fraction of writeout throughput which is very rare in general but frequent for example for FUSE bdis. To fix this problem we have to make sure write section of the sequence counter is irqsafe.

Which versions are affected by CVE-2026-23168?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-23168?

Apply the vendor's patch.

Is CVE-2026-23168 being exploited?

There is no known exploitation of CVE-2026-23168 in the wild and no public exploit code.

All Linux kernel vulnerabilities

Sources

Also known as AZL-77733, BELL-CVE-2026-23168, DEBIAN-CVE-2026-23168, GHSA-7xmm-c998-f7c9, ROOT-OS-UBUNTU-2404-CVE-2026-23168, UBUNTU-CVE-2026-23168.