CVE-2024-23848: Linux Kernel Use-After-Free Vulnerability

CVE-2024-23848 Overview

CVE-2024-23848 is a use-after-free vulnerability in the Linux kernel through version 6.7.1. The flaw exists in the cec_queue_msg_fh function within the Consumer Electronics Control (CEC) subsystem, specifically affecting drivers/media/cec/core/cec-adap.c and drivers/media/cec/core/cec-api.c. This vulnerability allows a local attacker with low privileges to trigger a denial of service condition by exploiting improper memory management in the CEC message queue handling.

Critical Impact

A local attacker can exploit this use-after-free vulnerability to cause system instability or denial of service on affected Linux systems with CEC functionality enabled.

Affected Products

• Linux Kernel versions through 6.7.1
• Systems with CEC (Consumer Electronics Control) functionality enabled
• Media subsystem components in drivers/media/cec/core/

Discovery Timeline

• 2024-01-23 - CVE-2024-23848 published to NVD
• 2025-05-30 - Last updated in NVD database

Technical Details for CVE-2024-23848

Vulnerability Analysis

This use-after-free vulnerability (CWE-416) occurs in the Linux kernel's Consumer Electronics Control (CEC) subsystem. The CEC protocol is used for communication between devices connected via HDMI, allowing them to control each other. The vulnerability manifests when memory that has been freed is subsequently accessed during message queue operations.

The flaw specifically affects the cec_queue_msg_fh function, which handles queuing of CEC messages for file handles. When a CEC adapter is being used and messages are being processed, a race condition or improper lifecycle management can lead to accessing memory after it has been deallocated.

Exploitation requires local access to the system and the ability to interact with CEC devices or interfaces. While the attack complexity is low once local access is obtained, the impact is limited to availability—causing system crashes or denial of service conditions.

Root Cause

The root cause of CVE-2024-23848 is improper memory lifecycle management in the CEC subsystem's message handling code. When CEC messages are queued via cec_queue_msg_fh, the code may reference memory structures that have already been freed during adapter cleanup or file handle closure operations. This typically occurs due to:

• Insufficient synchronization between message queue operations and adapter/file handle cleanup
• Missing reference counting on memory structures used across the CEC core and API layers
• Race conditions between concurrent operations on CEC file handles

Attack Vector

The attack vector for this vulnerability is local, requiring an attacker to have low-privilege access to the affected Linux system. The attack scenario involves:

1. An attacker with local system access interacts with the CEC subsystem through device files or system calls
2. By manipulating the timing of CEC operations or triggering specific sequences of adapter and file handle operations, the attacker can cause the use-after-free condition
3. When the freed memory is accessed, it can lead to kernel crashes, system instability, or denial of service

The vulnerability affects systems where CEC functionality is enabled, which is common on systems with HDMI connectivity used for media applications. No user interaction is required beyond the initial local access.

For technical details on the vulnerability mechanism, see the Kernel Mailing List Discussion.

Detection Methods for CVE-2024-23848

Indicators of Compromise

• Unexpected kernel crashes or panics with stack traces referencing cec_queue_msg_fh, cec-adap.c, or cec-api.c
• Kernel log messages indicating use-after-free conditions in the media/cec subsystem
• System instability when CEC-enabled devices are connected or CEC operations are performed
• KASAN (Kernel Address Sanitizer) reports flagging UAF in CEC-related code paths

Detection Strategies

• Enable KASAN (Kernel Address Sanitizer) to detect use-after-free conditions at runtime
• Monitor kernel logs (dmesg, /var/log/kern.log) for CEC subsystem errors or memory corruption warnings
• Deploy kernel-level monitoring tools that can detect anomalous memory access patterns
• Use SentinelOne's kernel-level protection to identify exploitation attempts targeting memory corruption vulnerabilities

Monitoring Recommendations

• Implement centralized logging for kernel messages across Linux endpoints
• Configure alerts for kernel panic events or unexpected system reboots
• Monitor for processes interacting with CEC device files (/dev/cec*)
• Enable audit logging for access to CEC-related system interfaces

How to Mitigate CVE-2024-23848

Immediate Actions Required

• Update the Linux kernel to a patched version that addresses CVE-2024-23848
• If immediate patching is not possible, consider disabling CEC functionality if not required
• Restrict local access to the system to trusted users only
• Monitor systems for signs of exploitation attempts

Patch Information

The vulnerability was reported through the Linux Kernel Mailing List. Users should update to a patched kernel version that includes the fix for the use-after-free condition in cec_queue_msg_fh. Check your distribution's security advisories for specific patched kernel versions:

• Review the Kernel Mailing List Discussion for technical details on the fix
• Monitor your Linux distribution's security channels for backported patches
• Consider using long-term support (LTS) kernel versions that receive security updates

Workarounds

• Disable the CEC kernel module if CEC functionality is not required: modprobe -r cec
• Blacklist the CEC module to prevent automatic loading: add blacklist cec to /etc/modprobe.d/blacklist.conf
• Restrict access to CEC device files using file permissions or SELinux/AppArmor policies
• Implement network segmentation to limit local access to affected systems

# Disable CEC module if not needed
sudo modprobe -r cec

# Blacklist CEC module to prevent loading at boot
echo "blacklist cec" | sudo tee /etc/modprobe.d/blacklist-cec.conf

# Verify the module is not loaded
lsmod | grep cec