CVE-2023-54139 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
tracing/user_events: Ensure write index cannot be negative
The write index indicates which event the data is for and accesses a per-file array. The index is passed by user processes during write() calls as the first 4 bytes. Ensure that it cannot be negative by returning -EINVAL to prevent out of bounds accesses.
Update ftrace self-test to ensure this occurs properly.
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Analysis
by VulDB Data Team • 01/03/2026
The vulnerability identified as CVE-2023-54139 resides within the Linux kernel's tracing subsystem, specifically in the user_events functionality that manages event data collection and processing. This flaw represents a critical issue in kernel space memory management where improper validation of user-provided data can lead to arbitrary code execution or system instability. The vulnerability is classified under CWE-129 as an "Improper Validation of Array Index" which directly impacts the kernel's ability to safely handle user-supplied indices during event logging operations.
The technical implementation of this vulnerability stems from the tracing/user_events subsystem where the write index parameter is used to determine which event data should be processed and stored in a per-file array structure. During write() system calls, user processes provide the first four bytes as the index value that indicates which event the data corresponds to. The flaw occurs when this index value is not properly validated to ensure it remains within acceptable bounds, allowing negative values to be processed. This negative index value can then be used to access memory locations outside the intended array boundaries, creating potential for memory corruption and privilege escalation.
The operational impact of CVE-2023-54139 extends beyond simple memory access violations as it represents a potential pathway for privilege escalation attacks within the Linux kernel environment. When a negative write index is processed, the kernel's memory management subsystem can be manipulated to access arbitrary memory locations, potentially allowing malicious actors to read sensitive kernel data, modify critical kernel structures, or even execute arbitrary code with kernel privileges. This vulnerability directly impacts the integrity and confidentiality of the Linux kernel's tracing functionality and can compromise the entire system's security posture. The issue is particularly concerning in environments where user processes have access to tracing interfaces, as it provides a potential attack vector for privilege escalation.
The kernel maintainers addressed this vulnerability by implementing proper validation of the write index parameter to ensure it cannot be negative, returning -EINVAL to prevent out of bounds accesses that could lead to memory corruption. This fix specifically targets the tracing/user_events subsystem and includes updates to the ftrace self-test framework to ensure proper validation occurs during kernel operation. The mitigation strategy follows established security principles by implementing input validation at the kernel boundary where user data enters the trusted execution environment, aligning with the ATT&CK technique T1068 which focuses on local privilege escalation through kernel vulnerabilities. The fix ensures that any attempt to provide a negative index value results in immediate rejection of the operation rather than allowing potentially harmful memory accesses to proceed, thereby maintaining the integrity of the kernel's memory management subsystem and protecting against unauthorized privilege escalation attacks.