GNU libidn before 1.44 is prone to out-of-bounds reads of uninitialized memory in the ToUnicode APIs because of mishandling in idna_to_unicode_internal. The affected code is not present in libidn2.
Exploitability
AV:LAC:HPR:NUI:NScope
S:UImpact
C:NI:LA:L4/CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:LOther