CVE-2026-23451: Linux Kernel Bonding Driver DoS Flaw

CVE-2026-23451 Overview

CVE-2026-23451 is a vulnerability in the Linux kernel's bonding driver that can cause a potential infinite loop in the bond_header_parse() function. The vulnerability exists when a stack of two bonding devices is configured, as skb->dev always points to the hierarchy top, causing the recursion to never terminate properly.

Critical Impact
Systems with stacked bonding network interfaces may experience denial of service conditions due to an infinite loop in kernel space, potentially causing system hangs or crashes.

Affected Products

Linux kernel (bonding driver subsystem)
Systems utilizing stacked bonding network configurations
Network infrastructure relying on bonded interfaces

Discovery Timeline

2026-04-03 - CVE CVE-2026-23451 published to NVD
2026-04-07 - Last updated in NVD database

Technical Details for CVE-2026-23451

Vulnerability Analysis

This vulnerability affects the Linux kernel's network bonding subsystem, specifically the bond_header_parse() function. The bonding driver allows multiple network interfaces to be combined into a single logical interface for redundancy or increased throughput. When bonding devices are stacked (one bonding device using another bonding device as a slave), the header parsing function can enter an infinite loop.

The root issue lies in how the function traverses the device hierarchy during header parsing operations. The skb->dev pointer consistently references the top of the device hierarchy rather than iterating through the stack properly, preventing the recursion from reaching a termination condition.

Root Cause

The bond_header_parse() function lacks proper bounds checking for recursive device traversal. When processing network packets on stacked bonding interfaces, the function's recursive logic fails to properly descend the device hierarchy because skb->dev always references the topmost device. This creates a scenario where the same device is processed repeatedly, resulting in an infinite loop within kernel space.

Attack Vector

The vulnerability can be triggered when:

A system is configured with stacked bonding devices (a bonding interface using another bonding interface as a member)
Network traffic requiring header parsing is processed through the stacked configuration
The bond_header_parse() function is invoked and enters an infinite loop

The fix adds a new const struct net_device *dev parameter to the (struct header_ops)->parse() method, ensuring the recursion is properly bounded and the final leaf parse method is correctly invoked.

Detection Methods for CVE-2026-23451

Indicators of Compromise

System experiencing unexpected hangs or freezes during network operations
Kernel soft lockup warnings in system logs referencing bonding driver functions
High CPU utilization in kernel space with no corresponding userspace activity
Network interfaces becoming unresponsive on systems with stacked bonding configurations

Detection Strategies

Monitor for kernel soft lockup messages in /var/log/kern.log or dmesg output containing references to bond_header_parse
Implement system monitoring for unusual CPU patterns in kernel space, particularly on systems with bonding configurations
Review network configurations to identify stacked bonding device setups that may be vulnerable
Use kernel tracing tools like ftrace to monitor bonding driver function calls and detect anomalous behavior

Monitoring Recommendations

Configure alerting for kernel panic or soft lockup events related to networking subsystems
Monitor system uptime and unexpected reboots on servers with bonding configurations
Implement watchdog timers to detect and recover from kernel-level hangs
Track kernel module loading and version information to ensure patched versions are deployed

How to Mitigate CVE-2026-23451

Immediate Actions Required

Review current network configurations to identify any stacked bonding device setups
Apply kernel patches from the official Linux kernel repositories as soon as they are available for your distribution
Consider temporarily flattening stacked bonding configurations to eliminate the vulnerable code path
Monitor affected systems closely for signs of exploitation or instability

Patch Information

The Linux kernel development team has released patches to address this vulnerability. The fix modifies the (struct header_ops)->parse() method signature to include a new const struct net_device *dev parameter, ensuring proper recursion bounds and correct invocation of the leaf parse method.

Relevant kernel commits are available:

Workarounds

Avoid creating stacked bonding configurations where one bonding interface uses another bonding device as a slave
If stacked bonding is required, limit network traffic types that would trigger header parsing through the affected code path
Consider using alternative network redundancy solutions such as LACP with a single layer of bonding
Implement network segmentation to limit exposure of vulnerable systems

bash

# Check for existing bonding configurations
cat /proc/net/bonding/*

# Identify stacked bonding devices
ip link show type bond

# Review bonding slave relationships
cat /sys/class/net/bond*/bonding/slaves