CVE-2025-68752: Linux Kernel Use-After-Free Vulnerability

CVE-2025-68752 Overview

A NULL pointer dereference vulnerability has been identified in the Linux kernel's iavf (Intel Adaptive Virtual Function) network driver. The vulnerability exists in the PTP (Precision Time Protocol) clock subsystem where ptp_clock_settime() assumes every ptp_clock has implemented the settime64() function. When this function is called on the iavf driver without a proper implementation, it results in a NULL pointer dereference, potentially causing a kernel panic or system crash.

Critical Impact

This vulnerability can cause kernel crashes and denial of service conditions on systems using Intel Adaptive Virtual Function network interfaces with PTP clock functionality.

Affected Products

• Linux Kernel (iavf driver)
• Systems using Intel Adaptive Virtual Function network interfaces
• Environments utilizing PTP clock synchronization with iavf NICs

Discovery Timeline

• 2026-01-05 - CVE-2025-68752 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2025-68752

Vulnerability Analysis

This vulnerability is a Null Pointer Dereference in the Linux kernel's iavf network driver. The issue arises from an incomplete implementation of the PTP clock interface. The ptp_clock_settime() function in the kernel's PTP subsystem expects all registered PTP clock devices to have a valid settime64() callback function. However, the iavf driver registered a PTP clock without implementing this required callback, leaving a NULL function pointer in the operations structure.

When user-space applications or kernel subsystems attempt to set the PTP clock time via ptp_clock_settime(), the kernel attempts to invoke the settime64() callback through the function pointer. Since this pointer is NULL in the iavf driver, the kernel dereferences NULL, resulting in an immediate kernel panic or oops condition.

Root Cause

The root cause is the missing implementation of the settime64() callback function in the iavf driver's PTP clock operations structure. The PTP clock subsystem was designed with the assumption that all clock drivers would implement this function, but the iavf driver omitted it, leaving a NULL pointer where a valid function address was expected. This is a common pattern of API contract violation where a driver fails to implement all required interface methods.

Attack Vector

The attack vector requires local access to the system. An attacker with the ability to interact with PTP clock devices (typically requiring root privileges or CAP_SYS_TIME capability) can trigger the vulnerability by calling the clock_settime() system call on the PTP clock device exposed by the iavf driver. While this limits the attack surface, any local process with appropriate privileges can cause a denial of service condition by crashing the kernel.

The fix implements a stub function that returns -EOPNOTSUPP (Operation not supported), gracefully rejecting the request instead of crashing. This approach mirrors the fix applied in commit 329d050bbe63 for the gve driver which had an identical issue.

Detection Methods for CVE-2025-68752

Indicators of Compromise

• Kernel panic messages referencing NULL pointer dereference in PTP clock operations
• System crashes occurring during PTP clock time synchronization operations
• Kernel oops logs showing call traces through ptp_clock_settime() or related PTP functions
• Unexpected system reboots on hosts using iavf network interfaces with PTP enabled

Detection Strategies

• Monitor kernel logs (dmesg, /var/log/kern.log) for NULL pointer dereference messages associated with the iavf or PTP subsystems
• Implement kernel crash dump analysis to identify the specific vulnerability trigger
• Use kernel tracing tools (ftrace, eBPF) to monitor calls to PTP clock operations on iavf devices
• Deploy system monitoring to detect repeated kernel panics or unexpected reboots

Monitoring Recommendations

• Enable kernel crash dump collection (kdump) to capture diagnostic information when crashes occur
• Configure alerting for kernel oops or panic events in centralized logging systems
• Monitor system uptime metrics for anomalies indicating crash/reboot cycles
• Review PTP-related application logs for unexpected failures or timeouts

How to Mitigate CVE-2025-68752

Immediate Actions Required

• Update the Linux kernel to a patched version that includes the fix for CVE-2025-68752
• If immediate patching is not possible, consider disabling PTP functionality on iavf interfaces until patched
• Restrict access to PTP clock devices to only essential services and trusted users
• Monitor systems using iavf drivers for any signs of instability or crashes

Patch Information

The Linux kernel maintainers have released patches to address this vulnerability. The fix implements a stub settime64() function that returns -EOPNOTSUPP, preventing the NULL pointer dereference while properly indicating the operation is not supported.

Patches are available in the following kernel commits:

• Kernel Git Commit 1e43ebc
• Kernel Git Commit 6d080f8
• Kernel Git Commit 9e3dbc3

Workarounds

• Restrict PTP clock device access using file permissions or SELinux/AppArmor policies
• Disable PTP functionality on affected iavf network interfaces if not required
• Use network segmentation to limit exposure of systems with vulnerable configurations
• Consider using alternative network drivers if PTP functionality is critical and patching is delayed

# Check if iavf driver is loaded
lsmod | grep iavf

# Check kernel version for patch status
uname -r

# Review PTP clock devices on the system
ls -la /dev/ptp*

# Restrict PTP device access (temporary workaround)
chmod 600 /dev/ptp*