Medium [CVE-2026-72330] Consume empty data records in tls_sw_read_sock

In the Linux kernel, the following vulnerability has been resolved: net/tls: Consume empty data records in tls_sw_read_sock() A peer may send a zero-length TLS application_data record; TLS 1.3 explicitly permits these as a traffic-analysis countermeasure (RFC 8446, Section 5.1).

After decryption such a record has full_len == 0. tls_sw_read_sock() hands it to the read_actor, which has no payload to consume and returns zero.

The loop treats a zero return as backpressure (used <= 0), requeues the skb at the head of rx_list, and stops. rx_list is serviced head-first on the next call, so the empty record is dequeued, fails the same way, and is requeued again; every later record on the connection is blocked behind it. tls_sw_recvmsg() does not stall on this: a zero-length data record copies nothing and falls through to consume_skb().

Mirror that in the read_sock() path by recognizing an empty data record before the actor runs, consuming it, and continuing. A flaw was found in the Linux kernel's TLS (Transport Layer Security) implementation.

A remote attacker could send specially crafted zero-length TLS application data records. This could cause the system to repeatedly process these empty records, blocking all subsequent legitimate data on the connection and leading to a Denial of Service (DoS).