In iperf before 3.19.1, iperf_auth.c has a Base64Decode assertion failure and application exit upon a malformed authentication attempt.
https://lists.debian.org/debian-lts-announce/2025/08/msg00020.html
https://github.com/esnet/iperf/releases/tag/3.19.1
https://github.com/esnet/iperf/commit/4eab661da0bbaac04493fa40164e928c6df7934a