docx4j's "PropertyResolver" and several adjacent helpers recursively walk the OpenXML style inheritance chain ("w:basedOn") without cycle detection. A WordprocessingML document containing a cyclic style chain (for example, Style A based on B and Style B based on A) causes unbounded recursion and a "java.lang.StackOverflowError" within the property-resolution code path. These helpers are used by operations that require effective style resolution, including common conversion and TOC-related paths. As a result, most server-side pipelines that accept a user-supplied docx and process it through docx4j can likely be crashed by a file containing a cyclic style reference.