CVE-2025-37747 perf: Fix hang while freeing sigtrap event

What is CVE-2025-37747?

CVE-2025-37747 is a medium-severity denial of service vulnerability in Linux kernel, published on 1 May 2025. 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: Fix hang while freeing sigtrap event

Perf can hang while freeing a sigtrap event if a related deferred signal hadn't managed to be sent before the file got closed:

perf_event_overflow() task_work_add(perf_pending_task)

fput() task_work_add(____fput())

task_work_run() ____fput() perf_release() perf_event_release_kernel() _free_event() perf_pending_task_sync() task_work_cancel() -> FAILED rcuwait_wait_event()

Once task_work_run() is running, the list of pending callbacks is removed from the task_struct and from this point on task_work_cancel() can't remove any pending and not yet started work items, hence the task_work_cancel() failure and the hang on rcuwait_wait_event().

Task work could be changed to remove one work at a time, so a work running on the current task can always cancel a pending one, however the wait / wake design is still subject to inverted dependencies when remote targets are involved, as pictured by Oleg:

T1 T2

fd = perf_event_open(pid => T2->pid); fd = perf_event_open(pid => T1->pid); close(fd) close(fd) <IRQ> <IRQ> perf_event_overflow() perf_event_overflow() task_work_add(perf_pending_task) task_work_add(perf_pending_task) </IRQ> </IRQ> fput() fput() task_work_add(____fput()) task_work_add(____fput())

task_work_run() task_work_run() ____fput() ____fput() perf_release() perf_release() perf_event_release_kernel() perf_event_release_kernel() _free_event() _free_event() perf_pending_task_sync() perf_pending_task_sync() rcuwait_wait_event() rcuwait_wait_event()

Therefore the only option left is to acquire the event reference count upon queueing the perf task work and release it from the task work, just like it was done before 3a5465418f5f ("perf: Fix event leak upon exec and file release") but without the leaks it fixed.

Some adjustments are necessary to make it work:

* A child event might dereference its parent upon freeing. Care must be taken to release the parent last.

* Some places assuming the event doesn't have any reference held and therefore can be freed right away must instead put the reference and let the reference counting to its job.

Which versions are affected by CVE-2025-37747?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2025-37747?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2025-37747 being exploited?

There is no known exploitation of CVE-2025-37747 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

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

Also known as AZL-69674, AZL-69680, BELL-CVE-2025-37747, DEBIAN-CVE-2025-37747, GHSA-g7p4-4259-746x, ROOT-OS-DEBIAN-12-CVE-2025-37747 and 3 more.