CVE-2026-68300

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

sctp: auth: verify auth requirement when auth_chunk is NULL

sctp_auth_chunk_verify() returns true unconditionally when

chunk->auth_chunk is NULL, silently skipping authentication.

This is incorrect when:

1. skb_clone() failed in the BH receive path, leaving auth_chunk

NULL. In sctp_endpoint_bh_rcv() asoc is NULL for new

connections, so the early sctp_auth_recv_cid() check cannot

catch this.

2. No AUTH chunk precedes COOKIE-ECHO, so skb_clone() is never

called and auth_chunk remains NULL.

Fix by checking sctp_auth_recv_cid() when auth_chunk is NULL:

if authentication is required, return false to drop the chunk;

otherwise continue normally.