Uncontrolled resource consumption vulnerability in the XML catalog processing logic of the libxml2 library. The issue arises when handling chains of XML catalogs that contain repeated <nextCatalog> elements pointing to the same downstream catalog. During entity resolution, the parser redundantly traverses catalog chains, causing exponential growth in processing time as depth increases. This can be exploited by supplying crafted catalogs to cause excessive CPU consumption and degrade application availability, resulting in a denial-of-service condition.