CVE-2026-64556 perf/core: Detach event groups during remove_on_exec
A race condition in the Linux kernel perf subsystem can corrupt PMU context lists, leading to a system crash or denial of service.
- 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-2026-64556?
CVE-2026-64556 is a high-severity vulnerability in Linux, published on 29 Jul 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/core: Detach event groups during remove_on_exec
perf_event_remove_on_exec() removes events by calling perf_event_exit_event(). For top-level events, this removes the event from the context with DETACH_EXIT only.
This can leave inconsistent group state when a removed event is a group leader and the group contains siblings without remove_on_exec. If the group was active, the surviving siblings can remain active and attached to the removed leader's sibling list, but are no longer represented by a valid group leader on the PMU context active lists.
A later close of the removed leader uses DETACH_GROUP and can promote the still-active siblings from this stale group state. The next schedule-in can then add an already-linked active_list entry again, corrupting the PMU context active list.
With DEBUG_LIST enabled, this is caught as a list_add double-add in merge_sched_in().
Fix this by detaching group relationships when remove_on_exec removes an event. This preserves the existing task-exit and revoke behavior, while ensuring surviving siblings are ungrouped before the removed event leaves the context.
Weakness: CWE-662
Which versions are affected by CVE-2026-64556?
How do I fix CVE-2026-64556?
Apply the vendor's patch.
Is CVE-2026-64556 being exploited?
There is no known exploitation of CVE-2026-64556 in the wild and no public exploit code.
Sources
Also known as AZL-94139, BELL-CVE-2026-64556, DEBIAN-CVE-2026-64556, GHSA-mpx2-cmqf-859j, ROOT-OS-DEBIAN-12-CVE-2026-64556, UBUNTU-CVE-2026-64556.