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:

1. A system is configured with stacked bonding devices (a bonding interface using another bonding interface as a member)
2. Network traffic requiring header parsing is processed through the stacked configuration
3. 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:

• Kernel Commit 4172a7901cf4
• Kernel Commit 946bb6cacf0c
• Kernel Commit 9b49c854f14f
• Kernel Commit b7405dcf7385

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

# 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