High [CVE-2026-74753] Reject exited events as group leaders

In the Linux kernel, the following vulnerability has been resolved: perf: Reject exited events as group leaders perf_event_remove_on_exec() sets remove-on-exec events to the EXIT state and detaches their group relationships.

The event's file descriptor can remain open, however, and perf_event_open() currently accepts that event as a group leader because its early validation rejects only REVOKED and DEAD events. A new sibling can consequently be linked to the detached leader.

When the leader is closed, perf_group_detach() observes that its PERF_ATTACH_GROUP bit is already clear and skips the new sibling. The sibling then retains a group_leader pointer to the freed event.

Perform the check while holding the shared context mutex so that an exec in the target task cannot detach the leader between validation and group attachment. [peterz: make the earlier test fully consistent] A flaw was found in the Linux kernel's performance monitoring (perf) subsystem.

This vulnerability allows a local attacker to trigger a use-after-free condition by improperly handling exited events as group leaders. Successful exploitation could lead to a system crash, resulting in a denial of service (DoS), or potentially enable an attacker to escalate privileges.

Red Hat severity: Important — CVSS 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-825.