CVE-2026-74637
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk2th percentile - higher than 2% of all known CVEs
Summary
A use-after-free vulnerability was found in the Linux kernel's perf subsystem, related to improper sibling event detachment from a group. When a sibling event is detached (e.g., during CPU hot-unplug), its group_leader pointer remains pointing to the old leader, which may be freed, leading to dereferencing freed memory during a PERF_IOC_FLAG_GROUP ioctl. The issue was reproduced by running the perf event fuzzer, CPU hotplug, and a stress workload concurrently.
Risk Assessment
An attacker with local access (e.g., via fuzzing or a malicious process) could cause a system crash (kernel panic) or potentially escalate privileges by exploiting the freed kernel memory. The vulnerability affects systems with perf events enabled and CPU hotplug capability.
Recommendation
Apply the official Linux kernel patch that fixes the issue by promoting the detached sibling to a singleton and fixing cgroup accounting in __event_disable(). Update the system to a kernel version containing the fix.
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In the Linux kernel XFS filesystem, during directory tree repair, a self-referential directory may be detected. In such a case, the repair code attempts to lock the same inode twice (double iolock/ilock), leading to a deadlock. The fix detects this corner case and handles it appropriately.
- CVE-2026-80533Unknown
In the Linux kernel XFS filesystem, during AGI repair, the function xrep_iunlink_walk_ondisk_bucket may attempt to use the pointer sc->sa.agi_bp, which can be null if the buffer verifier fails. The fix uses ragi->agi_bp instead, which skips verifier checks, to avoid walking off the end of memory.
Original NVD description (English source)
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.