CVE-2026-89478

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

sctp: drop a chunk if its transport was removed

sctp_rcv() resolves the transport once per packet and leaves it in

chunk->transport. The lookup reference, or the one sctpaddbacklog() takes

if the socket is owned by userspace, keeps it around until the chunk has

been processed.

An authenticated ASCONF DEL-IP can remove it in the meantime.

sctpassocrm_peer() takes the transport out of the association and calls

sctptransportfree(), which tags it dead and drops the reference the

association held. There is a window on both paths: the packet can sit on

the socket backlog, and on the direct path the lookup completes before

bhlocksock().

The DATA chunk in that packet puts the removed transport back into

asoc->peer.lastdatafrom. Once the packet is done that reference goes

away and the transport is freed by RCU, so the next delayed SACK carries

the pointer into the SACK chunk and sctpoutqselect_transport() reads the

freed transport's state.

Drop the chunk in sctpinqpush(), next to the existing rcvr->dead check.

Both paths reach it with the association's socket lock held. The peer

retransmits it.