SACK can cause extensive memory use via fragmented resend queue

A flaw in Linux kernel's TCP handling allows a remote attacker to send specially crafted network packets that cause excessive memory use and crash the system. The issue happens when the system tries to reassemble fragmented data using SACK (Selective Acknowledgment) sequences.

The vulnerability exists in tcp_fragment() where improper handling of SACK sequences causes pathological fragmentation of the TCP retransmission queue. A remote attacker can exploit this via specially crafted TCP packets to exhaust memory and trigger a denial of service, affecting all unpatched kernel versions prior to the listed fixes.