parser.c in libxml2 before 2.9.5 mishandles parameter-entity references because the NEXTL macro calls the xmlParserHandlePEReference function in the case of a '%' character in a DTD name.
https://www.oracle.com//security-alerts/cpujul2021.html
https://lists.debian.org/debian-lts-announce/2017/11/msg00041.html
https://github.com/GNOME/libxml2/commit/e26630548e7d138d2c560844c43820b6767251e3