CVE-2025-71226: Linux Kernel iwlwifi PTP Vulnerability

CVE-2025-71226 Overview

A vulnerability has been identified in the Linux kernel's Intel WiFi (iwlwifi) driver affecting the Precision Time Protocol (PTP) clock registration functionality. The issue stems from missing settime64 callback implementation in both MVM (Mac Virtual Machine) and MLD (Multi-Link Device) PTP clock implementations, which became a requirement following kernel commit dfb073d32cac.

When attempting to register the PTP clock through ptp_clock_register(), the absence of the ptp_clock_info.settime64 callback triggers kernel warnings and causes the PHC (Physical Hardware Clock) clock registration to fail with error code -22 (EINVAL). This impacts WiFi interface initialization and PTP functionality on affected Intel wireless devices.

Critical Impact

Intel WiFi interfaces using iwlwifi driver may fail to properly initialize PTP clock functionality, potentially affecting time synchronization capabilities and generating kernel warnings during interface startup.

Affected Products

• Linux kernel iwlwifi driver (MVM module)
• Linux kernel iwlwifi driver (MLD module)
• Systems with Intel WiFi hardware utilizing PTP clock functionality

Discovery Timeline

• 2026-02-18 - CVE CVE-2025-71226 published to NVD
• 2026-02-18 - Last updated in NVD database

Technical Details for CVE-2025-71226

Vulnerability Analysis

This vulnerability is a Driver Vulnerability affecting the Linux kernel's Intel wireless networking driver. The root issue emerged after upstream kernel changes tightened the requirements for PTP clock registration. Specifically, commit dfb073d32cac introduced a mandatory check that requires all PTP clocks to implement the ptp_clock_info.settime64 callback function.

The iwlwifi driver's MVM and MLD implementations register PTP clocks for hardware timestamping and time synchronization purposes. However, these implementations did not include a settime64 handler, as there was no appropriate firmware interface available to support this functionality. When the kernel's PTP subsystem validates the clock registration, it now returns -EINVAL when this required callback is NULL.

The practical impact includes kernel warnings being generated during WiFi interface startup (observable through wpa_supplicant process logs) and failure to register the PHC clock, which may degrade or disable PTP-based time synchronization capabilities for the wireless interface.

Root Cause

The root cause is a missing implementation of the settime64 callback function in the ptp_clock_info structure for both MVM and MLD PTP clock implementations within the iwlwifi driver. This callback became mandatory following changes to the PTP subsystem validation logic in the Linux kernel.

The iwlwifi driver developers noted that there is no appropriate firmware interface available to properly implement the settime64() functionality for setting absolute time on the hardware clock. Without this firmware support, a full implementation is not feasible.

Attack Vector

This is not a remotely exploitable vulnerability in the traditional security sense. The impact is primarily operational, affecting system stability and functionality rather than security. The vulnerability manifests locally during WiFi interface initialization when the iwlwifi driver attempts to register its PTP clock.

The affected code path is triggered through the iwl_mvm_ptp_init() function which calls ptp_clock_register(). Without local system access or specific hardware conditions (Intel WiFi hardware with PTP support), this issue cannot be triggered.

Detection Methods for CVE-2025-71226

Indicators of Compromise

• Kernel warning messages containing ptp_clock_register and iwl_mvm_ptp_init in system logs
• Error messages indicating "Failed to register PHC clock (-22)" from the iwlwifi driver
• wpa_supplicant process triggering warnings in drivers/ptp/ptp_clock.c

Detection Strategies

• Monitor kernel logs (dmesg or /var/log/kern.log) for PTP clock registration failures from iwlwifi
• Check for WARNING traces originating from ptp_clock.c:325 during WiFi interface startup
• Review system logs for iwlwifi-related errors with return code -22 (EINVAL)

Monitoring Recommendations

• Implement log monitoring for iwlwifi driver errors during system boot and WiFi interface activation
• Configure alerting on kernel warning patterns related to PTP subsystem failures
• Monitor WiFi interface initialization success rates on systems with Intel wireless hardware

How to Mitigate CVE-2025-71226

Immediate Actions Required

• Update to a patched Linux kernel version that includes the settime64 stub implementation
• If patching is not immediately possible, the warnings can be ignored as they do not indicate a security vulnerability
• Review and apply kernel updates from your Linux distribution's security channels

Patch Information

The fix implements a stub settime64 function that returns -EOPTNOTSUPP (operation not supported). This satisfies the PTP subsystem's requirement for the callback to exist while acknowledging that the functionality is not available on this hardware. Two kernel commits address this issue:

• Kernel Git Commit 81d90d93d22c
• Kernel Git Commit ff6892ea544c

Workarounds

• No configuration-based workarounds are available; the fix requires a kernel update
• The warnings generated do not indicate a security issue and can be safely ignored until patching is completed
• Consider disabling PTP functionality in iwlwifi if not required (requires kernel rebuild or module parameter if available)

# Verify kernel version after patching
uname -r

# Check for iwlwifi PTP-related errors in kernel logs
dmesg | grep -i "ptp\|iwlwifi\|phc"

# Monitor for registration issues
journalctl -k | grep -i "ptp_clock_register"