CVE-2024-50241 in Linux
Summary
by MITRE • 11/09/2024
In the Linux kernel, the following vulnerability has been resolved:
NFSD: Initialize struct nfsd4_copy earlier
Ensure the refcount and async_copies fields are initialized early. cleanup_async_copy() will reference these fields if an error occurs in nfsd4_copy(). If they are not correctly initialized, at the very least, a refcount underflow occurs.
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Analysis
by VulDB Data Team • 07/16/2025
The vulnerability identified as CVE-2024-50241 resides within the Linux kernel's Network File System Daemon implementation, specifically affecting the nfsd4_copy function that handles asynchronous copy operations between NFSv4 servers. This flaw represents a critical race condition and improper initialization issue that can lead to system instability and potential privilege escalation. The vulnerability occurs during the processing of NFSv4 copy operations where the struct nfsd4_copy structure is not properly initialized before being referenced in error handling paths.
The technical root cause stems from insufficient initialization of critical fields within the nfsd4_copy structure, namely the refcount and async_copies fields. When an error condition occurs during the execution of nfsd4_copy(), the cleanup_async_copy() function attempts to reference these uninitialized fields, creating a scenario where the reference counting mechanism can become corrupted. This improper initialization directly violates the principles of secure coding practices and can result in undefined behavior within the kernel's memory management subsystem. The vulnerability manifests as a potential refcount underflow, where the reference counter drops below zero due to improper initialization, leading to memory corruption and system instability.
The operational impact of this vulnerability extends beyond simple system crashes to potentially enable privilege escalation attacks within the kernel space. When the reference count underflows, it can cause memory corruption that attackers might exploit to gain elevated privileges or cause denial of service conditions that affect the entire system. The vulnerability affects systems running Linux kernel versions where the NFSv4 server implementation is active, particularly those utilizing NFSv4 copy operations for file transfers. This flaw aligns with CWE-665 Improper Initialization and CWE-476 NULL Pointer Dereference categories, representing a classic case of uninitialized memory access that can cascade into more severe security implications.
Mitigation strategies for CVE-2024-50241 require immediate kernel updates that ensure proper initialization of the nfsd4_copy structure fields before any error handling paths are executed. System administrators should prioritize patching affected systems, particularly those running NFSv4 services with copy operations enabled. The fix involves modifying the nfsd4_copy function to initialize the refcount and async_copies fields early in the function execution, preventing the cleanup_async_copy() function from accessing uninitialized memory. Organizations should also implement monitoring for NFSv4 copy operations and consider disabling unnecessary NFSv4 features when not required. This vulnerability demonstrates the importance of proper resource management in kernel space and aligns with ATT&CK techniques related to privilege escalation and system exploitation through kernel vulnerabilities. The fix represents a defensive programming approach that prevents the specific error path leading to reference count corruption while maintaining the intended functionality of the NFSv4 copy operations.