In imapscantreerecursive in Claws Mail through 3.17.6, a malicious IMAP server can trigger stack consumption because of unlimited recursion into subdirectories during a rebuild of the folder tree.

common/session.c in Claws Mail before 3.17.6 has a protocol violation because suffix data after STARTTLS is mishandled.

Stack-based buffer overflow in the conveuctojis function in codeconv.c in Claws Mail 3.13.1 allows remote attackers to have unspecified impact via a crafted email, involving Japanese character set conversion. NOTE: this vulnerability exists because of an incomplete fix for CVE-2015-8614.

Multiple stack-based buffer overflows in the (1) convjistoeuc, (2) conveuctojis, and (3) convsjistoeuc functions in codeconv.c in Claws Mail before 3.13.1 allow remote attackers to have unspecified impact via a crafted email, involving Japanese character set conversion.

plugins/rssyl/feed.c in Claws Mail before 3.10.0 disables the CURLOPTSSLVERIFYHOST check for CN or SAN host name fields, which makes it easier for remote attackers to spoof servers and conduct man-in-the-middle (MITM) attacks.