radicale is vulnerable to timing attacks. It does not compare passwords in constant time, because it uses a non-constant character to character comparison. Consequently, the comparison will fail faster when the first characters in the password are incorrect. Attackers can exploit this difference to perform a timing attack, essentially allowing them to guess the password one character at a time.
bugs.debian.org/861514
bugs.debian.org/cgi-bin/bugreport.cgi?bug=861514
github.com/Kozea/Radicale/blob/1.1.2/NEWS.rst
github.com/Kozea/Radicale/commit/059ba8dec1f22ccbeab837e288b3833a099cee2d
github.com/Kozea/Radicale/commit/190b1dd795f0c552a4992445a231da760211183b
lists.debian.org/debian-lts-announce/2020/04/msg00019.html