CVE-2026-23014: Linux Kernel Race Condition Vulnerability

CVE-2026-23014 Overview

A race condition vulnerability has been discovered in the Linux kernel's performance monitoring subsystem (perf). The vulnerability exists in the software event (swevent) high-resolution timer (hrtimer) handling code, where improper timer cancellation during event cleanup can lead to a use-after-free condition. The issue arises when hrtimer_try_to_cancel() is called in perf_swevent_cancel_hrtimer(), but the timer may still be active when the associated perf event structure is freed.

Critical Impact

Local attackers with access to the performance monitoring subsystem can potentially trigger a use-after-free condition, which may lead to privilege escalation, denial of service, or arbitrary code execution in kernel context.

Affected Products

• Linux Kernel (versions with affected perf subsystem code)
• Systems utilizing perf software events with high-resolution timers
• Linux distributions with vulnerable kernel versions

Discovery Timeline

• 2026-01-28 - CVE CVE-2026-23014 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2026-23014

Vulnerability Analysis

This vulnerability represents a classic race condition in the Linux kernel's perf subsystem timer management. The perf subsystem uses high-resolution timers (hrtimers) for software events to generate periodic interrupts for profiling purposes. When a perf event is being destroyed, the kernel attempts to cancel any associated timers through perf_swevent_cancel_hrtimer().

The root issue is that hrtimer_try_to_cancel() is a non-blocking call that may return without successfully canceling the timer if the timer callback is currently executing. In this scenario, the event structure can be freed while the timer callback is still referencing it, resulting in a use-after-free condition.

The fix involves installing a proper perf_event::destroy handler that performs a full hrtimer_cancel() on the free path. Unlike hrtimer_try_to_cancel(), hrtimer_cancel() will block until the timer callback completes, ensuring safe cleanup.

Root Cause

The vulnerability stems from insufficient synchronization between timer callback execution and event structure deallocation. The change to use hrtimer_try_to_cancel() in the timer cancellation path introduced a window where the timer could remain active while the event memory is being freed. The kernel's perf subsystem lacked a proper destroy handler to guarantee complete timer teardown before memory deallocation.

Attack Vector

An attacker with local access and permissions to use the perf subsystem can exploit this vulnerability by rapidly creating and destroying perf events with software event timers. By timing the destruction to coincide with timer callback execution, the attacker can trigger the use-after-free condition. Successful exploitation requires:

1. Access to the perf_event_open syscall
2. Ability to create software events with hrtimer-based sampling
3. Precise timing to trigger the race condition between timer execution and event destruction

The vulnerability can potentially be exploited by repeatedly creating perf events, triggering timer callbacks, and immediately closing the event file descriptors to race against the timer teardown sequence.

Detection Methods for CVE-2026-23014

Indicators of Compromise

• Kernel oops or panic messages referencing perf_swevent functions
• Unexpected crashes in perf-related kernel code paths
• Memory corruption symptoms following perf event operations
• KASAN (Kernel Address Sanitizer) reports showing use-after-free in perf subsystem

Detection Strategies

• Enable KASAN in development/testing kernels to detect memory corruption issues
• Monitor kernel logs for oops messages involving hrtimer or perf_swevent functions
• Deploy kernel live patching solutions to track vulnerable code paths
• Use SentinelOne Singularity platform for behavioral detection of exploitation attempts

Monitoring Recommendations

• Configure syslog to alert on kernel panic or oops events
• Monitor for unusual patterns of perf_event_open syscalls followed by rapid file descriptor closes
• Implement audit rules for performance monitoring subsystem access
• Track kernel module loading and perf subsystem configuration changes

How to Mitigate CVE-2026-23014

Immediate Actions Required

• Apply the latest kernel security patches from your Linux distribution
• Restrict access to the perf subsystem using kernel.perf_event_paranoid sysctl
• Consider disabling unprivileged perf access if not required for operations
• Monitor systems for signs of exploitation attempts

Patch Information

The vulnerability has been addressed in kernel commits that install a proper perf_event::destroy handler ensuring hrtimer_cancel() is called on the free path. Patches are available in the kernel stable trees:

• Kernel Git Commit Details
• Kernel Git Commit Information

Organizations should update to patched kernel versions provided by their Linux distribution.

Workarounds

• Increase kernel.perf_event_paranoid to restrict perf access to privileged users only
• Use SELinux or AppArmor policies to limit which processes can access the perf subsystem
• Consider disabling the perf subsystem entirely if not required for production workloads
• Implement additional access controls for the perf_event_open syscall

# Configuration example
# Restrict perf_event access to root only
echo 3 > /proc/sys/kernel/perf_event_paranoid

# Make setting persistent across reboots
echo "kernel.perf_event_paranoid = 3" >> /etc/sysctl.conf
sysctl -p