There were two bugs where parameter-entity references could lead to an unexpected change of the input buffer in xmlParseNameComplex and xmlDictLookup being called with an invalid pointer. Percent sign in DTD Names ========================= The NEXTL macro used to call xmlParserHandlePEReference. When parsing "complex" names inside the DTD, this could result in entity expansion which created a new input buffer. The fix is to simply remove the call to xmlParserHandlePEReference from the NEXTL macro. This is safe because no users of the macro require expansion of parameter entities. - xmlParseNameComplex - xmlParseNCNameComplex - xmlParseNmtoken The percent sign is not allowed in names, which are grammatical tokens. - xmlParseEntityValue Parameter-entity references in entity values are expanded but this happens in a separate step in this function. - xmlParseSystemLiteral Parameter-entity references are ignored in the system literal. - xmlParseAttValueComplex - xmlParseCharDataComplex - xmlParseCommentComplex - xmlParsePI - xmlParseCDSect Parameter-entity references are ignored outside the DTD. - xmlLoadEntityContent This function is only called from xmlStringLenDecodeEntities and entities are replaced in a separate step immediately after the function call. This bug could also be triggered with an internal subset and double entity expansion. This fixes bug 766956 initially reported by Wei Lei and independently by Chromium's ClusterFuzz, Hanno Böck, and Marco Grassi. Thanks to everyone involved. xmlParseNameComplex with XML_PARSE_OLD10 ======================================== When parsing Names inside an expanded parameter entity with the XML_PARSE_OLD10 option, xmlParseNameComplex would call xmlGROW via the GROW macro if the input buffer was exhausted. At the end of the parameter entity's replacement text, this function would then call xmlPopInput which invalidated the input buffer. There should be no need to invoke GROW in this situation because the buffer is grown periodically every XML_PARSER_CHUNK_SIZE characters and, at least for UTF-8, in xmlCurrentChar. This also matches the code path executed when XML_PARSE_OLD10 is not set. This fixes bugs 781205 (CVE-2017-9049) and 781361 (CVE-2017-9050). Thanks to Marcel Böhme and Thuan Pham for the report. Additional hardening ==================== A separate check was added in xmlParseNameComplex to validate the buffer size.