CVE-2025-68789: Linux Kernel Use-After-Free Vulnerability

CVE-2025-68789 Overview

A use-after-free vulnerability has been discovered in the Linux kernel's hwmon ibmpex driver. The ibmpex_high_low_store() function retrieves driver data using dev_get_drvdata() and uses it without proper validation. This creates a race condition where the sysfs callback can be invoked after the data structure has been freed, resulting in a use-after-free condition that could lead to system instability or potential code execution.

Critical Impact
This use-after-free vulnerability in the Linux kernel's ibmpex hardware monitoring driver could allow local attackers to cause denial of service or potentially achieve privilege escalation through memory corruption.

Affected Products

Linux kernel (versions with ibmpex hwmon driver)

Discovery Timeline

2026-01-13 - CVE-2025-68789 published to NVD
2026-01-13 - Last updated in NVD database

Technical Details for CVE-2025-68789

Vulnerability Analysis

The vulnerability exists in the ibmpex hardware monitoring driver within the Linux kernel. The core issue is a Time-of-Check Time-of-Use (TOCTOU) race condition combined with insufficient validation of driver data. When ibmpex_high_low_store() is called, it retrieves a pointer to driver data using dev_get_drvdata(). However, if the device is being removed concurrently, the data structure may have already been freed by the time it is accessed, leading to a use-after-free condition.

This type of vulnerability occurs because the sysfs interface allows userspace to interact with kernel driver attributes at any time, including during driver teardown. Without proper synchronization or validation, the callback function can operate on stale or freed memory.

Root Cause

The root cause is the lack of a NULL check after retrieving driver data via dev_get_drvdata(), combined with improper ordering of operations in the device deletion path. The deletion path frees the data structure before the sysfs entries are removed, creating a window where callbacks can still be invoked against freed memory.

Attack Vector

An attacker with local access to the system could exploit this vulnerability by racing the device removal process with sysfs attribute access. By timing writes to the high/low store sysfs attributes during driver unloading, an attacker could trigger the use-after-free condition.

The vulnerability manifests in the ibmpex_high_low_store() function where driver data is accessed without validation. The fix addresses this by adding a NULL check after dev_get_drvdata() and reordering operations in the deletion path to prevent the TOCTOU race condition. For detailed technical implementation, refer to the Linux Kernel Commit 68d62e5.

Detection Methods for CVE-2025-68789

Indicators of Compromise

Kernel panic or oops messages referencing ibmpex_high_low_store in the stack trace
Unexpected system crashes or instability on systems with IBM Power Executive hardware monitoring enabled
Memory corruption indicators in kernel logs associated with hwmon subsystem

Detection Strategies

Monitor kernel logs for use-after-free errors or invalid memory access in hwmon drivers
Use kernel debugging tools like KASAN (Kernel Address Sanitizer) to detect memory safety violations
Audit systems for the presence of the ibmpex driver module (lsmod | grep ibmpex)

Monitoring Recommendations

Enable kernel crash dump collection (kdump) to capture diagnostic information during any kernel panics
Configure alerting on kernel oops messages related to hwmon or ibmpex components
Implement system stability monitoring to detect unexpected reboots or crashes

How to Mitigate CVE-2025-68789

Immediate Actions Required

Update the Linux kernel to a patched version that includes the fix for CVE-2025-68789
If immediate patching is not possible, consider disabling or blacklisting the ibmpex module if not required
Monitor systems running the vulnerable driver for signs of exploitation or instability

Patch Information

The Linux kernel maintainers have released patches addressing this vulnerability. Multiple commits have been made available across different kernel branches:

Apply the appropriate patch for your kernel version from your Linux distribution's package repository.

Workarounds

Blacklist the ibmpex module if IBM Power Executive hardware monitoring is not required: echo "blacklist ibmpex" >> /etc/modprobe.d/blacklist.conf
Restrict local access to trusted users only, as exploitation requires local system access
Use mandatory access control (SELinux/AppArmor) policies to limit sysfs access

bash

# Blacklist ibmpex module as a temporary workaround
echo "blacklist ibmpex" | sudo tee /etc/modprobe.d/ibmpex-blacklist.conf
sudo modprobe -r ibmpex 2>/dev/null || echo "Module not currently loaded"