CVE-2026-74637
Received Received - Intake

Use-After-Free in Linux Kernel perf/core

Publication date: 2026-08-22

Last updated on: 2026-08-22

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: perf/core: Fix group leader use-after-free after sibling detach perf_group_detach() handles leader and sibling detach differently. When the group leader is detached, all siblings are promoted to singleton events and their group_leader pointer is reset to themselves. When a sibling is detached, it is removed from the leader's sibling_list, but its group_leader pointer is left pointing at the old leader. That is harmless when the sibling is being closed and freed immediately, as in the DETACH_DEAD path. It is not safe when the sibling is detached but kept alive, such as during CPU hotplug with DETACH_GROUP. In that case the sibling is removed from the context, while its file descriptor can still keep it alive. A typical failing sequence is: - A group contains leader L and sibling S. - CPU hot-unplug detaches S with DETACH_GROUP, removing it from L->sibling_list but leaving S->group_leader == L. - L is later closed and freed. - A PERF_IOC_FLAG_GROUP ioctl on S follows S->group_leader and dereferences the freed leader. This was reproduced by running the perf event fuzzer, CPU hotplug, and a stress workload concurrently: Unable to handle kernel paging request at virtual address 006b6b6b6b6b6cdb CPU: 2 PID: 12489 Comm: perf_fuzzer 6.18.7 PREEMPT pc : perf_ioctl+0x34c/0xc68 x20: ffffff89a3fa2c70 x8 : 6b6b6b6b6b6b6b6b Code: 943c4a0e 340047a0 f9404a94 f9411e88 (f940b908) Call trace: perf_ioctl+0x34c/0xc68 (P) __arm64_sys_ioctl+0xa0/0xf4 invoke_syscall+0x58/0xe4 el0_svc_common+0xa8/0xdc do_el0_svc+0x1c/0x28 el0_svc+0x40/0xc0 el0t_64_sync_handler+0x68/0xdc el0t_64_sync+0x1c4/0x1c8 The fault happened in perf_ioctl(), where perf_event_for_each() follows the stale group_leader pointer and perf_event_for_each_child() then dereferences the freed leader's context. Fix the use-after-free by promoting the detached sibling to a singleton. Also fix __event_disable() cgroup accounting and event state change.

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Meta Information

Published
2026-08-22
Last Modified
2026-08-22
Generated
2026-08-22
AI Q&A
2026-08-22
EPSS Evaluated
N/A
NVD
CVE-2026-74637
EUVD
EUVD-2026-64574

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel 6.18.7

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability is a use-after-free flaw in the Linux kernel's perf subsystem. It occurs when a sibling event in a performance monitoring group is detached but its group_leader pointer is not properly updated. When the leader is later freed, the sibling still references it, leading to a crash when accessing the freed memory.

Detection Guidance

This vulnerability is specific to the Linux kernel's perf subsystem and requires kernel-level detection. Monitor kernel logs for oops or panic messages related to perf_ioctl or CPU hotplug events. Check for crashes with error messages like 'Unable to handle kernel paging request' or 'perf_ioctl+0x34c'. Use dmesg or journalctl to review kernel logs for suspicious activity.

Impact Analysis

This vulnerability can cause system crashes or kernel panics if exploited. An attacker with local access could trigger the flaw by manipulating perf events during CPU hotplug operations, potentially leading to denial-of-service conditions or privilege escalation.

Mitigation Strategies

Apply the latest kernel patches or updates that include the fix for this CVE. If immediate patching is not possible, consider disabling the perf subsystem if not required, or restrict access to perf_event_open system calls via kernel parameters or security modules like SELinux.

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