CVE-2023-2166 Overview
A null pointer dereference vulnerability was discovered in the Controller Area Network (CAN) protocol implementation within the Linux kernel. The flaw exists in net/can/af_can.c where the ml_priv member may not be initialized during the receive path of CAN frames. This vulnerability allows a local user to crash the system or potentially cause a denial of service condition.
Critical Impact
Local attackers can exploit this null pointer dereference to crash the Linux kernel, causing system instability and denial of service conditions on affected systems.
Affected Products
- Linux Kernel versions prior to the fix
- Linux Kernel 6.1 release candidates (rc1 through rc8)
- Linux Kernel 6.1 base release
Discovery Timeline
- April 19, 2023 - CVE-2023-2166 published to NVD
- February 5, 2025 - Last updated in NVD database
Technical Details for CVE-2023-2166
Vulnerability Analysis
This vulnerability is classified as a Null Pointer Dereference (CWE-476) in the Linux kernel's CAN protocol subsystem. The issue stems from improper initialization of the ml_priv structure during CAN frame reception. When CAN frames are processed through the receive path in net/can/af_can.c, the code assumes that ml_priv has been properly initialized. However, under certain conditions, this initialization may not occur, leading to a null pointer being dereferenced.
The CAN (Controller Area Network) protocol is widely used in automotive and industrial systems for communication between microcontrollers and devices. This vulnerability affects the networking stack component responsible for handling CAN protocol frames, making it particularly relevant for systems that utilize CAN bus communications.
Root Cause
The root cause of this vulnerability lies in the incomplete initialization logic within the CAN protocol's receive path. The ml_priv pointer, which is expected to reference private data associated with the CAN socket, is not properly validated or initialized before being accessed. This creates a scenario where the kernel code attempts to dereference a null pointer, triggering a kernel panic or system crash.
The affected code path fails to implement proper null checks before accessing the ml_priv member, violating the defensive programming principles that kernel code should follow. This oversight allows an attacker with local access to trigger the vulnerable code path and cause a denial of service.
Attack Vector
The vulnerability requires local access to exploit. An attacker must have the ability to interact with the CAN protocol subsystem on the target Linux system. The attack can be executed without requiring elevated privileges beyond standard user access, though the attacker does need valid local credentials.
The exploitation involves triggering CAN frame reception through the affected code path where ml_priv has not been initialized. This can be accomplished by creating specific network conditions or sending specially crafted CAN frames that exercise the vulnerable receive path. Upon successful exploitation, the kernel will attempt to dereference the null pointer, resulting in a kernel panic and system crash.
Detection Methods for CVE-2023-2166
Indicators of Compromise
- Unexpected kernel panics or system crashes related to CAN subsystem operations
- Kernel oops messages referencing net/can/af_can.c or related CAN protocol functions
- System logs showing null pointer dereference errors in network subsystem
- Repeated denial of service conditions affecting systems with CAN interfaces
Detection Strategies
- Monitor kernel logs for panic messages mentioning CAN protocol or af_can module
- Implement kernel crash dump analysis to identify null pointer dereference patterns
- Deploy endpoint detection solutions to identify exploitation attempts targeting the CAN subsystem
- Use SentinelOne's Linux agent to detect anomalous kernel behavior and crash patterns
Monitoring Recommendations
- Enable kernel logging verbosity for network subsystems on critical systems
- Configure crash dump collection for forensic analysis of any kernel panics
- Monitor system uptime and availability metrics for unexpected service interruptions
- Implement alerting for repeated system crashes on systems utilizing CAN protocols
How to Mitigate CVE-2023-2166
Immediate Actions Required
- Update affected Linux kernel to a patched version that addresses this vulnerability
- Review systems for CAN protocol usage and prioritize patching accordingly
- Consider restricting local user access on systems with CAN interfaces until patches are applied
- Monitor for exploitation attempts while awaiting patch deployment
Patch Information
The vulnerability has been addressed in updated Linux kernel versions. System administrators should consult the Linux Kernel Mailing List Post for detailed information about the fix and affected versions. Apply the appropriate kernel updates from your Linux distribution's security update channels.
Workarounds
- Disable or unload the CAN protocol module (can) if CAN functionality is not required on the system
- Restrict local user access to systems that must maintain CAN protocol functionality
- Implement network segmentation to isolate systems using CAN interfaces
- Consider using kernel live patching solutions if available for your distribution to minimize downtime
# Disable CAN module if not required
sudo modprobe -r can
sudo modprobe -r can_raw
# Add to blacklist to prevent automatic loading
echo "blacklist can" | sudo tee /etc/modprobe.d/blacklist-can.conf
echo "blacklist can_raw" | sudo tee -a /etc/modprobe.d/blacklist-can.conf
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
