A security issue was found in htmldoc v1.9.12 and before. A NULL pointer dereference in the function image_load_jpeg() in image.cxx may result in denial of service.
https://ubuntu.com/security/CVE-2021-23191
https://github.com/michaelrsweet/htmldoc/issues/415
https://github.com/michaelrsweet/htmldoc/commit/369b2ea1fd0d0537ba707f20a2f047b6afd2fbdc