CVE-2026-72021

In the Linux kernel, the following vulnerability has been resolved:

ipvs: use parsed transport offset in SCTP state lookup

set_sctp_state() reads the SCTP chunk header again in order to drive the

IPVS SCTP state table. For IPv6 it computes the offset with

sizeof(struct ipv6hdr), while the surrounding IPVS code uses iph.len from

ip_vs_fill_iph_skb(), where ipv6_find_hdr() has already skipped

extension headers and found the real transport header.

This makes the state machine read from the wrong offset for IPv6 SCTP

packets that carry extension headers. For example, an INIT packet with an

8-byte destination options header can be scheduled correctly by

sctp_conn_schedule(), but set_sctp_state() reads the first byte of the

SCTP verification tag as a DATA chunk type. The connection then moves

from NONE to ESTABLISHED instead of INIT1, gets the longer established

timeout, and updates the active/inactive destination counters

incorrectly. This happens even though the SCTP handshake has not

completed.

Use the parsed transport offset passed down from ip_vs_set_state() for

the SCTP chunk-header lookup. For IPv4 and IPv6 packets without

extension headers this preserves the existing offset.