CVE-2025-38563: In the Linux kernel, the following vulnerability has been resolved: perf/core: Prevent VMA split of buffer mappings The perf mmap code is careful ab...

Description

In the Linux kernel, the following vulnerability has been resolved: perf/core: Prevent VMA split of buffer mappings The perf mmap code is careful about mmap()'ing the user page with the ringbuffer and additionally the auxiliary buffer, when the event supports it. Once the first mapping is established, subsequent mapping have to use the same offset and the same size in both cases. The reference counting for the ringbuffer and the auxiliary buffer depends on this being correct. Though perf does not prevent that a related mapping is split via mmap(2), munmap(2) or mremap(2). A split of a VMA results in perf_mmap_open() calls, which take reference counts, but then the subsequent perf_mmap_close() calls are not longer fulfilling the offset and size checks. This leads to reference count leaks. As perf already has the requirement for subsequent mappings to match the initial mapping, the obvious consequence is that VMA splits, caused by resizing of a mapping or partial unmapping, have to be prevented. Implement the vm_operations_struct::may_split() callback and return unconditionally -EINVAL. That ensures that the mapping offsets and sizes cannot be changed after the fact. Remapping to a different fixed address with the same size is still possible as it takes the references for the new mapping and drops those of the old mapping.

Metrics

CVSS 3.1

7.8/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

0.36%

27.7th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Linux	Linux Kernel	>= 4.1, < 5.4.297
Linux	Linux Kernel	>= 5.5, < 5.10.241
Linux	Linux Kernel	>= 5.11, < 5.15.190
Linux	Linux Kernel	>= 5.16, < 6.1.148
Linux	Linux Kernel	>= 6.2, < 6.6.102
Linux	Linux Kernel	>= 6.7, < 6.12.42
Linux	Linux Kernel	>= 6.13, < 6.15.10
Linux	Linux Kernel	>= 6.16, < 6.16.1
Debian	Debian Linux	11.0

References

Timeline

Published: Aug 19, 2025
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2025-38563?

In the Linux kernel, the following vulnerability has been resolved: perf/core: Prevent VMA split of buffer mappings The perf mmap code is careful about mmap()'ing the user page with the ringbuffer and additionally the auxiliary buffer, when the event supports it. Once the first mapping is established, subsequent mapping have to use the same offset and the same size in both cases. The reference counting for the ringbuffer and the auxiliary buffer depends on this being correct. Though perf does not prevent that a related mapping is split via mmap(2), munmap(2) or mremap(2). A split of a VMA results in perf_mmap_open() calls, which take reference counts, but then the subsequent perf_mmap_close() calls are not longer fulfilling the offset and size checks. This leads to reference count leaks. As perf already has the requirement for subsequent mappings to match the initial mapping, the obvious consequence is that VMA splits, caused by resizing of a mapping or partial unmapping, have to be prevented. Implement the vm_operations_struct::may_split() callback and return unconditionally -EINVAL. That ensures that the mapping offsets and sizes cannot be changed after the fact. Remapping to a different fixed address with the same size is still possible as it takes the references for the new mapping and drops those of the old mapping.

How severe is CVE-2025-38563?

CVE-2025-38563 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 0.36% probability of exploitation in the next 30 days.

How do I fix CVE-2025-38563?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.