The imagetruecolortopalette function in ext/gd/gd.c in PHP before 5.6.25 and 7.x before 7.0.10 does not properly validate the number of colors, which allows remote attackers to cause a denial of service (select_colors allocation error and out-of-bounds write) or possibly have unspecified other impact via a large value in the third argument.
openwall.com/lists/oss-security/2016/09/02/9
rhn.redhat.com/errata/RHSA-2016-2750.html
www.php.net/ChangeLog-5.php
www.php.net/ChangeLog-7.php
www.securityfocus.com/bid/92755
www.securitytracker.com/id/1036680
bugs.php.net/bug.php?id=72697
github.com/php/php-src/commit/28022c9b1fd937436ab67bb3d61f652c108baf96
github.com/php/php-src/commit/b6f13a5ef9d6280cf984826a5de012a32c396cd4?w=1
security.gentoo.org/glsa/201611-22
www.tenable.com/security/tns-2016-19