CVE-2026-89753 mm/vmscan: report RCU-tasks quiescent states in shrink_lruvec()
A missing RCU quiescent state report in Linux kernel memory reclaim can cause RCU stalls and system hangs, requiring a kernel patch.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Not stated
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89753?
CVE-2026-89753 is a denial of service vulnerability in Linux, published on 11 Sep 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
mm/vmscan: report RCU-tasks quiescent states in shrink_lruvec()
I am seeing some rcu_tasks stalls in the Meta fleet during reclaim.
INFO: rcu_tasks detected stalls on tasks: 0000000088620d09: .. nvcsw: 6735/6735 holdout: 1 idle_cpu: -1/8 task:GlobalCPUThread state:R running task pid:2552016 tgid:2524552 Call Trace: shrink_lruvec mem_cgroup_iter shrink_node do_try_to_free_pages try_to_free_pages __alloc_frozen_pages_noprof alloc_pages_noprof pte_alloc_one __pte_alloc handle_mm_fault
Nothing promises direct reclaim returns in bounded time, and the scan loop in shrink_lruvec() only calls cond_resched(), which is a no-op on PREEMPTION kernels. Involuntary preemption is not a Tasks-RCU quiescent state, so the reclaiming task never reports one and becomes a holdout.
Upgrade it to cond_resched_tasks_rcu_qs(), which reports a quiescent state even when cond_resched() does nothing.
PS: This has been discussed in [1]
Which versions are affected by CVE-2026-89753?
How do I fix CVE-2026-89753?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-89753 being exploited?
There is no known exploitation of CVE-2026-89753 in the wild and no public exploit code.
Sources
Also known as AZL-100839, BELL-CVE-2026-89753, DEBIAN-CVE-2026-89753, GHSA-vf4v-9g5v-367g, UBUNTU-CVE-2026-89753.