CVE-2024-50259 in Linux
Summary
by MITRE • 11/09/2024
In the Linux kernel, the following vulnerability has been resolved:
netdevsim: Add trailing zero to terminate the string in nsim_nexthop_bucket_activity_write()
This was found by a static analyzer. We should not forget the trailing zero after copy_from_user() if we will further do some string operations, sscanf() in this case. Adding a trailing zero will ensure that the function performs properly.
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Analysis
by VulDB Data Team • 10/02/2025
The vulnerability identified as CVE-2024-50259 resides within the Linux kernel's netdevsim module, specifically in the nsim_nexthop_bucket_activity_write() function. This issue represents a classic buffer management flaw that can lead to undefined behavior when processing user-space input. The netdevsim module serves as a network simulation driver that allows developers to test network drivers and applications without requiring physical hardware, making it a critical component in kernel development and testing environments. The vulnerability manifests when the kernel attempts to process string data received from user space through the copy_from_user() function, which is a fundamental operation for safely transferring data between user and kernel space in Linux systems.
The technical flaw stems from insufficient string termination handling in the kernel's memory management operations. When copy_from_user() transfers data from user space to kernel space, it does not automatically append a null terminator to the destination buffer. In this specific case, the code subsequently passes the copied data to sscanf() for parsing operations, which requires null-terminated strings to function correctly. Without explicit null termination, sscanf() may read beyond the intended buffer boundaries, potentially accessing uninitialized memory or memory belonging to other data structures. This behavior violates fundamental kernel security principles and can result in unpredictable program execution, memory corruption, or information disclosure. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, though it specifically manifests as a string handling issue rather than a traditional buffer overflow.
The operational impact of this vulnerability extends beyond simple functionality degradation to potential security implications within kernel space. When the nsim_nexthop_bucket_activity_write() function processes malformed input, the lack of proper string termination can cause the kernel to behave unpredictably during string parsing operations. This could enable an attacker with local privileges to potentially manipulate kernel memory structures or cause system instability through denial-of-service conditions. The static analyzer that discovered this issue highlights a common class of vulnerabilities in kernel code where developers assume certain functions will handle string termination automatically, leading to subtle but dangerous oversights. Given that this affects the netdevsim module, which is often used in testing and development environments, the vulnerability could be exploited in scenarios where kernel modules are loaded or when testing network driver functionality.
Mitigation strategies for CVE-2024-50259 focus on ensuring proper string handling in kernel space operations. The fix implemented in the kernel involves explicitly adding a trailing zero character after copying data from user space to ensure proper string termination before subsequent string operations. This approach aligns with the ATT&CK framework's defensive techniques for kernel-mode exploitation prevention, specifically targeting the mitigation of information disclosure and memory corruption vulnerabilities. System administrators should ensure their kernels are updated to versions containing the fix, typically found in kernel releases following the identification of the vulnerability. Additionally, the fix demonstrates the importance of defensive programming practices in kernel development, where explicit null termination should be considered mandatory when dealing with string operations following memory copy operations. The vulnerability serves as a reminder of the critical importance of adhering to kernel security best practices and the value of static analysis tools in identifying subtle but potentially dangerous coding patterns. Regular kernel updates and proper security auditing of kernel modules remain essential defenses against such issues, particularly in environments where kernel modules are actively loaded or where testing scenarios involve user-space interaction with kernel components.