UBUNTU-CVE-2026-121968: High severity ubuntu/netrek-client-cow vulnerability

Netrek-client-cow through 3.3.3 contains an out-of-bounds read vulnerability in short.c handleSMessage() that allows malicious servers to crash clients via an unchecked mrecpt index. Attackers controlling a Netrek server or intercepting the plaintext TCP connection can send SPSMESSAGE packets with mrecpt of 36 or more, reading past players[] and shipnos to deny service.