CVE-2026-23313 Overview
A vulnerability has been discovered in the Linux kernel's i40e network driver that causes a preempt count leak in the NAPI poll tracepoint. The issue stems from improper use of get_cpu() in the tracepoint assignment without a corresponding put_cpu() call, leading to preemption count imbalance during soft interrupt handling.
Critical Impact
This vulnerability can cause system instability and potential denial of service conditions due to preemption count leaks in the network receive soft interrupt path, affecting systems using Intel i40e network adapters.
Affected Products
- Linux kernel with i40e network driver
- Systems using Intel Ethernet Controller X710/XL710 family adapters
- Linux distributions with affected kernel versions
Discovery Timeline
- March 25, 2026 - CVE CVE-2026-23313 published to NVD
- March 25, 2026 - Last updated in NVD database
Technical Details for CVE-2026-23313
Vulnerability Analysis
The vulnerability exists in the i40e driver's NAPI poll tracepoint implementation. When network packets are processed through the softirq mechanism, the driver incorrectly uses get_cpu() to retrieve the current processor ID within the tracepoint assignment code path. The function get_cpu() disables preemption and returns the current CPU number, but the corresponding put_cpu() call that should re-enable preemption is never executed.
This creates an asymmetric preemption count, as evidenced by kernel warning messages showing the preempt count changing from 00000100 to 00000101 during softirq processing. The NET_RX softirq path is particularly affected, causing the kernel to detect and report this inconsistency.
Root Cause
The root cause is a programming error in the tracepoint instrumentation code within the i40e driver. The developer used get_cpu() when they only needed the processor ID without disabling preemption. The correct function to use in this context is smp_processor_id(), which returns the current CPU number without modifying the preemption state.
The fix involves replacing get_cpu() with smp_processor_id() in the tracepoint assignment, eliminating the preemption count leak entirely.
Attack Vector
The attack vector for this vulnerability is currently unknown. However, the vulnerability manifests during normal network packet processing when:
- Network traffic arrives on an interface managed by the i40e driver
- The NAPI poll mechanism is invoked to process received packets
- Tracepoints are enabled for monitoring driver behavior
- The preemption count becomes unbalanced, potentially leading to system instability
The vulnerability can cause gradual system degradation as preemption counts accumulate incorrectly over time, potentially leading to soft lockups or other denial of service conditions on systems under heavy network load.
Detection Methods for CVE-2026-23313
Indicators of Compromise
- Kernel warning messages containing "huh, entered softirq 3 NET_RX with preempt_count" in system logs
- Preemption count mismatch warnings during network operations
- System instability or soft lockups on systems with i40e network adapters
- Degraded network performance under high traffic loads
Detection Strategies
- Monitor kernel logs (dmesg) for softirq preemption count warnings
- Deploy monitoring for i40e driver-specific error messages
- Implement kernel tracing to detect preemption count anomalies
- Use SentinelOne Singularity platform to monitor for kernel-level anomalies and stability issues
Monitoring Recommendations
- Enable kernel logging at appropriate verbosity levels to capture softirq warnings
- Configure alerting for preemption count leak messages in centralized log management systems
- Monitor system uptime and stability metrics on affected systems
- Track i40e driver events through kernel event monitoring tools
How to Mitigate CVE-2026-23313
Immediate Actions Required
- Update the Linux kernel to a patched version containing the fix
- If unable to immediately patch, consider disabling i40e tracepoints temporarily
- Monitor affected systems for signs of instability
- Plan maintenance windows for kernel updates on production systems
Patch Information
The fix has been committed to the stable Linux kernel tree. The patch replaces the problematic get_cpu() call with smp_processor_id() in the tracepoint assignment code. Multiple kernel commits address this issue:
- Kernel Git Commit Update
- Kernel Git Commit Fix
- Kernel Git Commit Security Patch
- Kernel Git Commit Improvement
Administrators should apply the appropriate patch for their kernel version from the stable kernel repository.
Workarounds
- Disable i40e driver tracepoints if not required for debugging purposes
- Reduce network load on affected systems until patches can be applied
- Consider using alternative network drivers if available for your hardware
- Implement system monitoring to detect and respond to stability issues promptly
# Configuration example
# Disable i40e tracepoints temporarily (if available)
echo 0 > /sys/kernel/debug/tracing/events/i40e/enable
# Verify current kernel version
uname -r
# Check for available kernel updates
apt-get update && apt-cache policy linux-image-generic
# or for RHEL/CentOS
yum check-update kernel
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
