CVE-2023-54039 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
can: j1939: j1939_tp_tx_dat_new(): fix out-of-bounds memory access
In the j1939_tp_tx_dat_new() function, an out-of-bounds memory access could occur during the memcpy() operation if the size of skb->cb is larger than the size of struct j1939_sk_buff_cb. This is because the memcpy() operation uses the size of skb->cb, leading to a read beyond the struct j1939_sk_buff_cb.
Updated the memcpy() operation to use the size of struct j1939_sk_buff_cb instead of the size of skb->cb. This ensures that the memcpy() operation only reads the memory within the bounds of struct j1939_sk_buff_cb, preventing out-of-bounds memory access.
Additionally, add a BUILD_BUG_ON() to check that the size of skb->cb is greater than or equal to the size of struct j1939_sk_buff_cb. This ensures that the skb->cb buffer is large enough to hold the j1939_sk_buff_cb structure.
[mkl: rephrase commit message]
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Analysis
by VulDB Data Team • 12/26/2025
The vulnerability identified as CVE-2023-54039 resides within the Linux kernel's CAN (Controller Area Network) subsystem, specifically affecting the J1939 protocol implementation. This issue manifests in the j1939_tp_tx_dat_new() function where a critical out-of-bounds memory access condition can occur during memory copy operations. The flaw represents a fundamental security weakness that could potentially be exploited to compromise system integrity and stability.
The technical root cause stems from an improper memory management operation within the kernel's networking stack. During the execution of memcpy() operations, the system utilizes the size parameter derived from skb->cb rather than the intended struct j1939_sk_buff_cb size. This mismatch creates a scenario where memory reads extend beyond the allocated bounds of the target structure, potentially exposing sensitive kernel memory regions to unauthorized access patterns. The vulnerability specifically targets the J1939 transport layer implementation which handles message transmission over CAN networks, making it particularly concerning for automotive and industrial control systems that rely heavily on this protocol.
This memory access violation poses significant operational risks to systems utilizing the Linux kernel's CAN networking capabilities. The out-of-bounds read could lead to information disclosure, system instability, or potentially enable privilege escalation attacks depending on the execution context. Given that J1939 protocol is widely used in automotive applications, industrial automation, and marine systems, the impact extends beyond typical server environments to critical infrastructure components where system reliability and security are paramount. The vulnerability demonstrates a classic buffer over-read condition that aligns with CWE-125, which specifically addresses out-of-bounds read vulnerabilities in software systems.
The kernel developers have implemented a comprehensive fix that addresses both the immediate memory access issue and establishes preventive measures for future occurrences. The primary solution involves updating the memcpy() operation to utilize the correct structure size of j1939_sk_buff_cb instead of relying on the potentially larger skb->cb size. This change ensures that memory operations remain strictly within the bounds of the intended data structure. Additionally, the implementation includes a BUILD_BUG_ON() directive that performs compile-time validation to verify that the skb->cb buffer is sufficiently large to accommodate the j1939_sk_buff_cb structure. This proactive approach prevents similar issues from emerging in future kernel versions and aligns with security best practices outlined in the ATT&CK framework's defense evasion techniques, particularly those targeting kernel-level memory corruption vulnerabilities.
The fix demonstrates proper defensive programming practices and follows established kernel security guidelines for memory management operations. By implementing both runtime and compile-time checks, the solution addresses not only the immediate vulnerability but also strengthens the overall robustness of the kernel's CAN subsystem. This remediation approach reflects the importance of maintaining proper data structure boundaries in kernel space operations and highlights the critical nature of memory safety in operating system components that handle network communications and industrial protocols. The vulnerability resolution ensures that systems relying on J1939 transport layer functionality can maintain their security posture while continuing to support critical automotive and industrial applications.