CVE-2026-93181 perf/x86/intel/uncore: Fix uncore_box ref/unref ordering
A race condition in the Linux kernel's Intel uncore performance monitoring driver can cause improper resource teardown, leading to a 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-2026-93181?
CVE-2026-93181 is a vulnerability in Linux, published on 17 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:
perf/x86/intel/uncore: Fix uncore_box ref/unref ordering
In uncore_event_cpu_online(), uncore_box_ref() was called before uncore_change_context(). uncore_box_ref() gates on box->cpu >= 0, but box->cpu is still -1 at that point because uncore_change_context() has not run yet. As a result, the box is never initialized on the first CPU to come online in a die, leaving it permanently uninitialized in the single-CPU-per-die case.
Thus, box->refcnt is one count below the true value, and in the CPU offline path, the box will be torn down on the second-to-last CPU.
In uncore_event_cpu_offline(), uncore_box_unref() was called after uncore_change_context(), so box->cpu is already -1 when the collector CPU goes offline, which prevents it from tearing down the box.
Fix by swapping the call order in both paths so that uncore_box_{ref,unref}() runs at the point where box->cpu reflects the correct context.
Move allocate_boxes() out of uncore_box_ref() to enable this reordering.
Which versions are affected by CVE-2026-93181?
How do I fix CVE-2026-93181?
Apply the vendor's patch.
Is CVE-2026-93181 being exploited?
There is no known exploitation of CVE-2026-93181 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-93181, DEBIAN-CVE-2026-93181, GHSA-79f3-6wm5-9qvc, UBUNTU-CVE-2026-93181.