CVE-2026-72376 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
afs: Fix misplaced inc of net->cells_outstanding
Fix net->cells_outstanding being incremented before the check for failure of idr_alloc_cyclic(), leaving the count incremented on error.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability in question affects the Andrew File System implementation within the Linux kernel, specifically concerning the management of network cell outstanding operations. This issue resides in the afs subsystem which provides support for the Andrew File System, a distributed file system that was originally developed at Carnegie Mellon University and later integrated into various Unix-like operating systems including Linux. The flaw manifests in how the kernel handles resource allocation and error conditions within the network cell management code path.
The technical root cause involves improper ordering of operations within the afs network cell handling logic where the net->cells_outstanding counter is incremented before a critical failure check occurs. This counter tracks the number of outstanding network operations for AFS cells, serving as a mechanism to monitor system load and resource usage. When the idr_alloc_cyclic() function fails during cell allocation, the increment operation has already been completed, leading to an inconsistent state where the counter remains incremented despite the operation ultimately failing. This represents a classic resource leak scenario where system accounting becomes out of sync with actual resource availability.
The operational impact of this vulnerability extends beyond simple counter corruption, as it can lead to misleading system monitoring data and potentially affect resource management decisions based on incorrect cell outstanding counts. In high-load environments where AFS is extensively used, this could result in inaccurate system performance metrics that might mask genuine resource exhaustion conditions or trigger inappropriate scaling behaviors. The flaw also creates potential issues for system administrators who rely on accurate counters for capacity planning and troubleshooting activities.
This vulnerability aligns with CWE-691, which addresses insufficient control flow management, specifically concerning improper ordering of operations that can lead to resource leaks and inconsistent state management. The issue demonstrates poor error handling practices where side effects occur before validation checks, violating fundamental principles of defensive programming. From an ATT&CK perspective, this could be categorized under privilege escalation techniques through resource manipulation, as incorrect accounting might enable attackers to exploit system resources more effectively than normal operations would allow.
Mitigation strategies should focus on correcting the operation ordering within the afs subsystem to ensure that resource counters are only incremented upon successful completion of allocation operations. The fix requires reordering the code logic so that idr_alloc_cyclic() failure checks occur before any increment operations on net->cells_outstanding. System administrators should ensure timely kernel updates are applied, particularly in environments heavily utilizing AFS services. Additionally, monitoring systems should be configured to detect unusual patterns in cell outstanding counters as potential indicators of similar resource management issues within the kernel's distributed file system subsystems.