CVE-2026-80727 x86/mce: Set up the polling timer before CMCI discovery

What is CVE-2026-80727?

CVE-2026-80727 is a vulnerability in Linux, published on 3 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:

x86/mce: Set up the polling timer before CMCI discovery

I hit the following on one of my machines:

mce: CPU0 BANK15 CMCI inherited storm ------------[ cut here ]------------ ODEBUG: assert_init not available (active state 0) object: (____ptrval____) object type: timer_list hint: 0x0 WARNING: lib/debugobjects.c:632 at debug_object_assert_init+0x178/0x230, CPU#0: swapper/0/0 CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.2.0-rc5 #3 PREEMPTLAZY RIP: 0010:debug_object_assert_init+0x18f/0x230 Call Trace: <TASK> __mod_timer mce_timer_kick cmci_discover intel_init_cmci mce_intel_feature_init mcheck_cpu_init identify_cpu identify_boot_cpu arch_cpu_finalize_init start_kernel

A second splat follows right after, from timer_setup() finding that same timer already queued:

ODEBUG: init active (active state 0) object: (____ptrval____) object type: timer_list hint: stub_timer+0x0/0x10

This is happening because CMCI storm detection is trying to modify the timer before latter was properly set up.

Set up the timer first. __mcheck_cpu_setup_timer() only calls timer_setup(), and depends on neither the generic nor the vendor init.

[ bp: Massage commit message. ]

Which versions are affected by CVE-2026-80727?

How do I fix CVE-2026-80727?

Apply the vendor's patch.

Is CVE-2026-80727 being exploited?

There is no known exploitation of CVE-2026-80727 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2026-80727, DEBIAN-CVE-2026-80727, GHSA-5fmr-wwgg-gfqm, UBUNTU-CVE-2026-80727.