CVE-2024-36020 in Linux
Summary
by MITRE • 05/30/2024
In the Linux kernel, the following vulnerability has been resolved:
i40e: fix vf may be used uninitialized in this function warning
To fix the regression introduced by commit 52424f974bc5, which causes servers hang in very hard to reproduce conditions with resets races. Using two sources for the information is the root cause. In this function before the fix bumping v didn't mean bumping vf pointer. But the code used this variables interchangeably, so stale vf could point to different/not intended vf.
Remove redundant "v" variable and iterate via single VF pointer across whole function instead to guarantee VF pointer validity.
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Analysis
by VulDB Data Team • 05/07/2026
The vulnerability CVE-2024-36020 addresses a critical uninitialized variable issue within the Linux kernel's i40e driver component that affects Intel Ethernet network adapters. This flaw manifests as a warning indicating that a virtual function (VF) pointer may be used uninitialized, representing a fundamental software engineering oversight that can lead to system instability and potential denial of service conditions. The issue specifically impacts systems utilizing the i40e driver for managing Intel 400 series Ethernet controllers and is classified under CWE-457 as "Use of Uninitialized Variable" which directly relates to improper initialization of variables in memory management contexts.
The technical root cause stems from a regression introduced by commit 52424f974bc5 that created a race condition scenario during hardware reset operations, resulting in server hangs under extremely difficult to reproduce conditions. The vulnerability arises from the improper handling of two separate data sources containing information about virtual functions, where the code previously used variables interchangeably without proper synchronization. This design flaw allowed stale VF pointers to reference unintended virtual functions, creating a scenario where the v variable and vf pointer were not consistently managed throughout the function execution. The issue demonstrates characteristics consistent with CWE-362, "Concurrent Execution using Shared Resource with Improper Synchronization," as multiple code paths were accessing the same resource without proper coordination mechanisms.
The operational impact of this vulnerability extends beyond simple warning messages to potentially catastrophic system behavior including complete server hangs and service disruption. The race condition conditions that trigger this vulnerability are particularly concerning because they occur during reset operations when the system is already under stress, making them extremely difficult to detect and reproduce in production environments. When the system encounters this condition, it may result in complete system lockups where the server becomes unresponsive to network traffic and administrative access, effectively creating a denial of service scenario that can impact critical infrastructure services. The intermittent nature of the bug makes it particularly dangerous as it may appear to function correctly during routine operations but fail catastrophically during high-stress scenarios such as hardware resets or rapid network traffic fluctuations.
Mitigation strategies should focus on implementing the recommended code fix that eliminates the redundant "v" variable and establishes a single, consistent VF pointer throughout the entire function execution cycle. This approach ensures proper pointer validity by removing the ambiguous variable usage patterns that created the race condition. System administrators should prioritize applying the kernel patch that resolves this vulnerability, particularly in production environments where network reliability is critical. The fix addresses the core issue by ensuring that all code paths within the function consistently reference the same VF pointer, thereby eliminating the possibility of stale pointer references. Additionally, organizations should implement comprehensive monitoring for system stability indicators during reset operations and consider implementing automated failover mechanisms to minimize service disruption if this vulnerability is encountered in unpatched systems. The solution aligns with ATT&CK technique T1499.004 "Endpoint Denial of Service" by addressing the underlying cause of system instability that could be exploited to create denial of service conditions through improper resource management.