CVE-2023-3159: Linux Kernel Use-After-Free Vulnerability

CVE-2023-3159 Overview

A use after free vulnerability was discovered in the Linux Kernel's FireWire driver, specifically in the outbound_phy_packet_callback function within drivers/firewire/core-cdev.c. This memory corruption flaw allows a local attacker with elevated privileges to trigger a use after free condition when the queue_event() function fails, potentially leading to system compromise.

Critical Impact

Local attackers with high privileges can exploit this use after free condition to achieve high impact on confidentiality, integrity, and availability of affected Linux systems.

Affected Products

• Linux Kernel versions prior to the security fix
• Linux Kernel 5.18 (including release candidates rc1 through rc5)
• Systems with FireWire (IEEE 1394) subsystem enabled

Discovery Timeline

• 2023-06-12 - CVE-2023-3159 published to NVD
• 2025-04-23 - Last updated in NVD database

Technical Details for CVE-2023-3159

Vulnerability Analysis

This vulnerability is classified as CWE-416 (Use After Free), a memory corruption issue where a program continues to use a pointer after the memory it references has been freed. In the context of the FireWire driver, the vulnerability occurs within the outbound_phy_packet_callback function when processing outbound PHY packets.

The flaw manifests when the queue_event() function fails during callback processing. Under normal operation, the callback handles packet completion events and manages associated memory structures. However, when queue_event() encounters a failure condition, improper memory management leads to a scenario where freed memory can be accessed, creating a use after free condition.

Successful exploitation requires local access and high privileges, but can result in complete compromise of confidentiality, integrity, and availability on the target system.

Root Cause

The root cause lies in the improper handling of the outbound_phy_packet_event structure lifecycle within the outbound_phy_packet_callback function. When queue_event() fails, the code path does not properly maintain a reference to the client structure before the packet event might be freed, leading to potential access of already deallocated memory.

Attack Vector

The attack requires local access to the system with elevated privileges. An attacker must be able to interact with the FireWire subsystem and trigger conditions that cause queue_event() to fail. This could be achieved through:

1. Manipulating system resources to cause memory allocation failures
2. Triggering race conditions in the FireWire driver
3. Exploiting the callback mechanism during high-load scenarios

The local attack vector combined with high privilege requirements limits the exposure, but successful exploitation can lead to kernel-level code execution or system instability.

// Security patch from drivers/firewire/core-cdev.c
// Fix: Store client reference before potential use after free
 {
 	struct outbound_phy_packet_event *e =
 		container_of(packet, struct outbound_phy_packet_event, p);
+	struct client *e_client;
 
 	switch (status) {
 	/* expected: */

Source: GitHub Linux Commit

The patch introduces a separate e_client variable to safely store the client reference, preventing access to potentially freed memory when the event structure is deallocated.

Detection Methods for CVE-2023-3159

Indicators of Compromise

• Unexpected kernel panics or oops messages referencing the FireWire driver or outbound_phy_packet_callback
• System instability when FireWire devices are connected or during high I/O operations on IEEE 1394 interfaces
• Kernel log entries showing memory corruption warnings in the drivers/firewire/ subsystem

Detection Strategies

• Monitor kernel logs (dmesg, /var/log/kern.log) for FireWire-related errors and memory warnings
• Deploy kernel-level monitoring tools to detect anomalous memory access patterns in the FireWire driver
• Use KASAN (Kernel Address Sanitizer) in development environments to identify use after free conditions
• Implement runtime memory debugging to catch invalid memory accesses in kernel modules

Monitoring Recommendations

• Configure alerting for kernel panic events that reference FireWire components
• Monitor system stability metrics and track unexplained crashes or restarts
• Review audit logs for suspicious privileged user activity targeting device drivers

How to Mitigate CVE-2023-3159

Immediate Actions Required

• Update the Linux Kernel to a version containing the security fix (commit b7c81f80246fac44077166f3e07103affe6db8ff)
• If immediate patching is not possible, consider disabling the FireWire subsystem if not required
• Restrict local access and limit users with elevated privileges that could potentially exploit this vulnerability
• Apply the principle of least privilege to reduce the attack surface

Patch Information

The vulnerability has been addressed in the official Linux Kernel repository. The fix is available in commit b7c81f80246fac44077166f3e07103affe6db8ff, which properly handles the client reference to prevent the use after free condition. System administrators should update to kernel versions that include this commit or apply the patch to their current kernel build.

For detailed patch information, refer to the official Linux kernel commit.

Workarounds

• Disable the FireWire kernel modules (firewire-core, firewire-ohci) if IEEE 1394 functionality is not required
• Blacklist FireWire modules to prevent automatic loading at system startup
• Implement strict access controls to limit privileged user accounts that could exploit kernel vulnerabilities

# Disable FireWire modules as a temporary workaround
# Add to /etc/modprobe.d/blacklist-firewire.conf
blacklist firewire-core
blacklist firewire-ohci
blacklist firewire-sbp2
blacklist firewire-net

# Unload currently loaded FireWire modules
sudo modprobe -r firewire-net firewire-sbp2 firewire-ohci firewire-core