High [CVE-2026-68300] verify auth requirement when auth_chunk is NULL

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.

A flaw was found in the Stream Control Transmission Protocol (SCTP) authentication mechanism within the Linux kernel. The `sctp_auth_chunk_verify()` function incorrectly processes authentication chunks, leading to authentication requirements being silently bypassed.

This can occur under specific conditions, such as when memory allocation fails or when an authentication chunk is missing before a COOKIE-ECHO message. An attacker could potentially exploit this to bypass intended security controls.

Red Hat severity: Moderate — CVSS 7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-303.