Queue Accounting Issue in Linux Kernel Impacting HFSC Functionality

CVE-2025-38000

What is CVE-2025-38000?

A vulnerability in the Linux Kernel exposes a queue accounting issue when handling packets with the Hierarchical Fair Service Curve (HFSC) class. This flaw arises during the enqueue operation, specifically in the hfsc_enqueue() function, where the queue length and backlog are not correctly updated before triggering a child queue's peek operation. As a result, the queue accounting can become inconsistent, potentially leading to unexpected behavior such as packet drops and use-after-free vulnerabilities. This vulnerability has been addressed by modifying the order of operations to ensure accurate queue metrics, preventing the risks associated with an improper accounting state.

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