CVE-2024-49999 in Linux
Summary
by MITRE • 10/21/2024
In the Linux kernel, the following vulnerability has been resolved:
afs: Fix the setting of the server responding flag
In afs_wait_for_operation(), we set transcribe the call responded flag to the server record that we used after doing the fileserver iteration loop - but it's possible to exit the loop having had a response from the server that we've discarded (e.g. it returned an abort or we started receiving data, but the call didn't complete).
This means that op->server might be NULL, but we don't check that before attempting to set the server flag.
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Analysis
by VulDB Data Team • 03/22/2026
The vulnerability identified as CVE-2024-49999 resides within the Linux kernel's Andrew File System (AFS) implementation, specifically affecting the afs_wait_for_operation() function. This flaw represents a critical issue in the kernel's handling of distributed file system operations where the server response flag management becomes inconsistent due to improper null pointer validation. The AFS subsystem operates as a distributed file system that allows clients to access files stored on remote servers through a unified namespace, making it a significant component in enterprise and high-performance computing environments where file system reliability is paramount.
The technical root cause of this vulnerability stems from a logic error in the fileserver iteration loop within the afs_wait_for_operation() function. During the execution of network operations, the system processes responses from multiple servers and attempts to update server records with response flags. However, the implementation fails to validate whether the op->server pointer remains valid before attempting to set the server responding flag. This condition can occur when the loop exits due to receiving a response that is subsequently discarded, such as when a server returns an abort signal or when data transmission begins but the complete call fails. The improper handling creates a scenario where the system attempts to dereference a potentially NULL pointer, leading to undefined behavior that could manifest as system instability or potential privilege escalation.
The operational impact of this vulnerability extends beyond simple system crashes, as it could enable malicious actors to exploit the NULL pointer dereference to disrupt AFS operations or potentially gain elevated privileges within the kernel space. The vulnerability affects systems running Linux kernels with AFS support, particularly those utilizing distributed file systems where multiple server responses are processed in iterative loops. From an ATT&CK perspective, this issue maps to T1068 (Exploitation for Privilege Escalation) and T1499 (Endpoint Denial of Service) as it could be leveraged to cause system instability or unauthorized access. The vulnerability's exploitation potential is heightened in environments where AFS is actively used for file sharing and where the system's integrity depends on proper handling of distributed server communications.
Mitigation strategies for CVE-2024-49999 should prioritize immediate kernel updates from vendors who have addressed this specific flaw in their patched releases. System administrators should monitor for security advisories from Linux distributions and apply patches promptly to prevent exploitation. The fix implemented in the patched kernel version involves adding proper NULL pointer validation before setting the server responding flag, ensuring that the op->server pointer is verified as non-null before any operations are performed on it. Additionally, organizations should implement monitoring solutions to detect anomalous AFS behavior or potential exploitation attempts, particularly in environments where AFS is extensively deployed. The fix aligns with CWE-476 which addresses NULL Pointer Dereference, and represents a standard defensive programming practice that prevents undefined behavior in kernel space operations. Regular security assessments of kernel components and proper access controls around AFS services can further reduce the risk surface associated with this type of vulnerability.