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.
