An issue has been found in libpng 1.6.34. It is a SEGV in the function png_free_data in png.c, related to the recommended error handling for png_read_image.
https://security.gentoo.org/glsa/201908-02
https://seclists.org/bugtraq/2019/Apr/30
https://github.com/glennrp/libpng/issues/238
https://github.com/fouzhe/security/tree/master/libpng
http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html
http://packetstormsecurity.com/files/152561/Slackware-Security-Advisory-libpng-Updates.html