When sending invalid base64 SASL data, login process is disconnected from the auth server, causing all active authentication sessions to fail. Invalid BASE64 data can be used to DoS a vulnerable server to break concurrent logins. Install fixed version or disable concurrency in login processes (heavy perfomance penalty on large deployments). No publicly available exploits are known.
1:2.4.1+dfsg1-5ubuntu4.1Exploitability
AV:NAC:LPR:NUI:NScope
S:UImpact
C:NI:NA:LCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L