xmlXPathNextPrecedingInternal(xmlXPathParserContextPtr ctxt,
                              xmlNodePtr cur)
{
    if ((ctxt == NULL) || (ctxt->context == NULL)) return(NULL);
    if (cur == NULL) {
        cur = ctxt->context->node;
        if (cur == NULL)
            return (NULL);
        if (cur->type == XML_NAMESPACE_DECL)
            return (NULL);
        ctxt->ancestor = cur->parent;
    }
    if ((cur->prev != NULL) && (cur->prev->type == XML_DTD_NODE))
	cur = cur->prev;
    while (cur->prev == NULL) {
        cur = cur->parent;
        if (cur == NULL)
            return (NULL);
        if (cur == ctxt->context->doc->children)
            return (NULL);
        if (cur != ctxt->ancestor)
            return (cur);
        ctxt->ancestor = cur->parent;
    }
    cur = cur->prev;
    while (cur->last != NULL)
        cur = cur->last;
    return (cur);
}

This vulnerability category highlights issues in resource management where failures to properly release memory, file handles, or other resources can degrade system performance or enable denial-of-service conditions.