CVE-2024-42076 is a vulnerability identified in the Linux kernel, specifically within the Controller Area Network (CAN) protocol stack implementation for J1939, a higher-layer protocol used in automotive and industrial environments. The issue arises in the function j1939_send_one(), which constructs a full CAN frame but fails to initialize certain unused data bytes within the frame. This results in a kernel information leak, as uninitialized kernel memory is inadvertently exposed to user space during socket operations involving raw_recvmsg(). The vulnerability was detected by syzbot, a kernel fuzzing tool, which reported kernel memory sanitizer (KMSAN) warnings indicating that uninitialized data was copied to user space. The root cause is that bytes 12-15 of a 16-byte data structure remain uninitialized before being sent to user space, potentially leaking sensitive kernel memory contents. The flaw is located in the CAN J1939 socket send path and affects Linux kernel versions prior to the patch. The vulnerability does not require authentication or special privileges beyond the ability to send or receive CAN J1939 messages, which may be accessible on systems with CAN interfaces enabled. Exploitation could allow local attackers or processes with access to CAN sockets to read uninitialized kernel memory, potentially disclosing sensitive information such as kernel pointers or other data that could aid in further attacks like privilege escalation or bypassing kernel security mitigations. The vulnerability has been fixed by initializing the previously unused data in j1939_send_one(), preventing the leak. No known exploits are reported in the wild as of the publication date. The vulnerability affects Linux kernel versions prior to the patch commit identified by the hash 9d71dd0c70099914fcd063135da3c580865e924c. The issue is relevant for systems using the CAN J1939 protocol, commonly found in automotive, industrial control, and embedded Linux environments.

For European organizations, the impact of CVE-2024-42076 depends on the deployment of Linux systems utilizing CAN J1939 interfaces. Industries such as automotive manufacturing, transportation, industrial automation, and critical infrastructure that rely on embedded Linux devices with CAN bus communication are most at risk. The information leak could expose kernel memory contents, potentially revealing sensitive data or kernel pointers that facilitate further exploitation, including privilege escalation or kernel address space layout randomization (KASLR) bypass. This could lead to unauthorized access, disruption of industrial control systems, or compromise of safety-critical automotive systems. Although exploitation requires local access to CAN J1939 sockets, many embedded or industrial devices run Linux kernels with CAN support enabled and may be accessible internally or via networked gateways. The leak undermines confidentiality and could be a stepping stone for attackers to gain deeper control over affected devices. European organizations operating connected vehicles, smart factories, or critical infrastructure with Linux-based CAN devices should consider this vulnerability a significant risk to operational security and safety. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits leveraging this information leak.

1. Apply the official Linux kernel patches that initialize unused data in j1939_send_one() as soon as they become available for your kernel version. Monitor vendor advisories for updated kernel packages. 2. For embedded or industrial Linux devices, coordinate with hardware and software vendors to ensure updated firmware or kernel versions are deployed promptly. 3. Restrict access to CAN J1939 sockets to trusted users and processes only. Implement strict access controls and use Linux capabilities or SELinux/AppArmor policies to limit socket creation and usage. 4. Disable CAN J1939 protocol support on systems where it is not required to reduce the attack surface. 5. Monitor system logs and network traffic for unusual CAN socket activity that may indicate attempts to exploit this vulnerability. 6. Conduct security audits of embedded Linux devices in operational environments to verify kernel versions and patch status. 7. For critical infrastructure and automotive environments, implement network segmentation and isolation to limit exposure of CAN interfaces to untrusted networks or users. 8. Employ runtime security tools that can detect anomalous kernel memory access or information leak attempts.