CVE-2026-72017 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
net: macb: drop in-flight Tx SKBs on close
The MACB driver has since forever leaked the outgoing SKBs that have not yet been marked as completed. They live in queue->tx_skb which gets freed without remorse nor checking.
macb_free_consistent() gets called in a few codepaths, but only close will trigger the added expressions. In macb_open() and macb_alloc_consistent() failure cases, queues' tx_skb just got allocated and are empty.
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Analysis
by VulDB Data Team • 09/02/2026
The vulnerability identified in the Linux kernel's MACB driver represents a critical memory management flaw that has persisted for an extended period within the network subsystem. This issue specifically affects the gigabit Ethernet driver used in various embedded systems and SoC platforms, where the driver fails to properly clean up transmit socket buffer structures during device closure operations. The problem manifests as a memory leak condition where outgoing packets that have been queued for transmission but not yet completed remain allocated in memory, creating a persistent resource drain that can accumulate over time. The technical root cause lies in the improper handling of the tx_skb array within the queue structure, which serves as the primary data structure for managing pending transmit operations.
The operational impact of this vulnerability extends beyond simple memory consumption, potentially leading to system instability and performance degradation in embedded environments where memory resources are constrained. When a network interface is closed or reconfigured, the driver should ensure all pending transmit operations are properly cleaned up before releasing allocated resources. However, the current implementation fails to check the queue->tx_skb array for pending packets during the macb_free_consistent() function call path that occurs exclusively during device closure. This oversight means that any transmit socket buffers that have been queued but not yet processed remain in memory, creating a cumulative leak that can eventually exhaust available resources and cause the system to become unresponsive or crash.
The fix implemented addresses this issue by adding specific checks within the macb_free_consistent() function that are only triggered during device close operations. This targeted approach ensures that pending transmit socket buffers are properly flushed before resource deallocation occurs, while avoiding unnecessary overhead in normal operational conditions. The solution follows established kernel development practices for memory management and resource cleanup, ensuring that all allocated resources are properly accounted for and released regardless of the code path taken through the driver's initialization and shutdown sequences. This vulnerability aligns with CWE-401, which specifically addresses improper release of memory after transfer of ownership, and could potentially be exploited by attackers to cause denial of service conditions through sustained resource exhaustion attacks.
The mitigation strategy focuses on maintaining proper resource accounting throughout the driver lifecycle while minimizing performance impact on normal operations. The added checks during device closure ensure that all pending transmit operations are properly completed or discarded before memory is freed, preventing the accumulation of stale socket buffer references. This approach aligns with industry best practices for kernel module development and follows the principle of least privilege in resource management, where resources are only released after ensuring they are no longer needed or referenced. The fix demonstrates the importance of comprehensive testing and code review processes in kernel development, particularly for drivers that manage critical system resources like network buffers. Organizations deploying affected systems should prioritize applying this patch to maintain system stability and prevent potential denial of service conditions that could arise from sustained memory consumption patterns.