Packet Dropping Issue in Linux Kernel's htcb Queuing Mechanism

CVE-2025-39766

What is CVE-2025-39766?

A vulnerability in the Linux Kernel allows packet dropping when specific conditions trigger an incorrect return value from the cake_enqueue function. This occurs under scenarios where the memory limit is set very low, leading to a buffer limit that inadvertently drops packets. The issue arises when the htb_activate function is called with an empty child queuing discipline, ultimately affecting network performance and flow management. Proper adjustments ensure that NET_XMIT_CN is returned to signal congestion when packets are dropped in these critical handling scenarios.

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