CVE-2026-23153: Linux Kernel Race Condition Vulnerability

CVE-2026-23153 Overview

A race condition vulnerability has been identified in the Linux kernel's FireWire (IEEE 1394) core subsystem. The vulnerability exists in the transaction list handling mechanism, where enumeration of the transaction list occurs without properly acquiring the card lock during AR (Asynchronous Receive) response event processing. This creates a race condition when AT (Asynchronous Transmit) request completion events are processed concurrently, potentially leading to system instability or denial of service conditions.

Critical Impact

This race condition in the Linux kernel FireWire subsystem could allow local attackers to trigger kernel instability or denial of service through concurrent transaction processing.

Affected Products

• Linux Kernel (versions with FireWire core subsystem)

Discovery Timeline

• 2026-02-14 - CVE CVE-2026-23153 published to NVD
• 2026-02-18 - Last updated in NVD database

Technical Details for CVE-2026-23153

Vulnerability Analysis

The vulnerability resides in the FireWire core subsystem's handling of concurrent transaction events. When the kernel processes AR response events, it enumerates the transaction list without holding the appropriate card lock. Simultaneously, AT request completion events may also access and modify this same transaction list. Without proper synchronization through locking mechanisms, this concurrent access creates a classic Time-of-Check Time-of-Use (TOCTOU) race condition.

The race window exists because the jiffies value in the card structure is read before the lock is acquired, allowing for potential state inconsistency between the time the transaction list is checked and when operations are performed on it. This can lead to corrupted transaction state, use of stale data, or accessing freed memory regions.

Root Cause

The root cause is improper synchronization in the FireWire core's transaction handling code. Specifically, the transaction list enumeration lacks the necessary card lock acquisition during AR response event processing. Additionally, the timer start operation for split transaction expiration was not properly enclosed within the lock scope, allowing race conditions with concurrent AT request completion processing.

Attack Vector

An attacker with local access to a system with FireWire hardware enabled could potentially exploit this race condition by:

1. Generating FireWire traffic that triggers multiple concurrent AR response and AT request completion events
2. Timing the transactions to maximize the probability of hitting the race window
3. Repeatedly attempting exploitation to trigger the race condition, potentially causing kernel instability or denial of service

The vulnerability requires local access and the presence of FireWire hardware or subsystem, which limits the attack surface but remains a concern for systems with FireWire interfaces enabled.

The fix addresses this by moving the timer start operation for split transaction expiration inside the protected lock scope, ensuring proper synchronization when accessing the transaction list and card structure values. The kernel commits 20e01bba2ae4898ce65cdcacd1bd6bec5111abd9 and b038874e31fc3caa0b0d5abd259dd54b918ad4a1 implement this correction.

Detection Methods for CVE-2026-23153

Indicators of Compromise

• Unexpected kernel panics or oops messages referencing FireWire or firewire-core modules
• System instability when FireWire devices are connected or active
• Kernel log entries showing warnings about list corruption or locking issues in FireWire subsystem
• Abnormal CPU usage patterns during FireWire transaction processing

Detection Strategies

• Monitor kernel logs for race condition warnings using dmesg | grep -i firewire or similar filtering
• Implement kernel module auditing to track FireWire subsystem activity
• Use kernel debugging tools such as lockdep to identify potential locking issues in the FireWire core module
• Deploy endpoint detection solutions capable of monitoring kernel-level anomalies

Monitoring Recommendations

• Enable kernel lockdep debugging during testing to identify synchronization issues
• Configure syslog forwarding for kernel messages to centralized SIEM systems
• Implement automated alerting on kernel panic events or FireWire-related warnings
• Regularly review system stability metrics on hosts with FireWire interfaces enabled

How to Mitigate CVE-2026-23153

Immediate Actions Required

• Update the Linux kernel to a patched version containing the fix commits
• If immediate patching is not possible, consider disabling the FireWire subsystem if not required for operations
• Monitor affected systems for signs of instability or exploitation attempts
• Review system logs for any anomalous FireWire-related activity

Patch Information

The vulnerability has been resolved in the Linux kernel with the following commits:

• Commit 20e01bba2ae4898ce65cdcacd1bd6bec5111abd9
• Commit b038874e31fc3caa0b0d5abd259dd54b918ad4a1

Organizations should apply the latest kernel updates from their distribution vendor that include these fixes. Check with your Linux distribution's security advisory channels for specific package versions containing the patch.

Workarounds

• Disable the FireWire subsystem by blacklisting the firewire-core module if FireWire functionality is not required
• Remove or disconnect FireWire hardware from affected systems as a temporary measure
• Implement access controls to limit local access to systems with FireWire interfaces
• Consider using virtualization to isolate systems requiring FireWire access

# Disable FireWire module by blacklisting
echo "blacklist firewire-core" | sudo tee /etc/modprobe.d/disable-firewire.conf
echo "blacklist firewire-ohci" | sudo tee -a /etc/modprobe.d/disable-firewire.conf

# Unload FireWire modules if currently loaded
sudo modprobe -r firewire-ohci
sudo modprobe -r firewire-core

# Verify modules are not loaded
lsmod | grep firewire