CVE-2026-23127

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

perf: Fix refcount warning on event->mmap_count increment

When calling refcount_inc(&event->mmap_count) inside perf_mmap_rb(), the

following warning is triggered:

refcount_t: addition on 0; use-after-free.

WARNING: lib/refcount.c:25

PoC:

struct perf_event_attr attr = {0};

int fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0);

mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

int victim = syscall(__NR_perf_event_open, &attr, 0, -1, fd,

PERF_FLAG_FD_OUTPUT);

mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, victim, 0);

This occurs when creating a group member event with the flag

PERF_FLAG_FD_OUTPUT. The group leader should be mmap-ed and then mmap-ing

the event triggers the warning.

Since the event has copied the output_event in perf_event_set_output(),

event->rb is set. As a result, perf_mmap_rb() calls

refcount_inc(&event->mmap_

Remediation

Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References