In LibSass prior to 3.5.5, functions inside ast.cpp for IMPLEMENT_AST_OPERATORS expansion allow attackers to cause a denial-of-service resulting from stack consumption via a crafted sass file, as demonstrated by recursive calls involving clone(), cloneChildren(), and copy().
https://github.com/sass/libsass/issues/2660
http://lists.opensuse.org/opensuse-security-announce/2019-08/msg00027.html
http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00051.html
http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00047.html