Bitcoin Core: peer can crash a node on Windows, macOS and BSD through TCP urgent data

According to Bitcoin Core's disclosure, platforms other than Linux use a select()-based socket monitoring backend that monitored exceptional socket conditions regardless of whether reading was paused. By sending TCP urgent (out-of-band) data, a malicious peer bypasses backpressure and forces the node to queue an unbounded amount of data; the source says that, in practice, this makes it trivial to crash any Windows, macOS or BSD node to which the attacker is connected. Severity is rated Medium; only the select() code path is affected, and Linux nodes are unaffected. Fixes were released in versions 29.5, 30.4, 31.2 and 32.1.