OpenPrinting CUPS before 2.4.20 contains a NULL pointer dereference caused by repeated IPP group tags in job-creation requests. IPP parsing creates unnamed separator attributes with IPP_TAG_ZERO, but add_job() converts these separators to IPP_TAG_JOB. During job startup, get_options()/ipp_length() subsequently calls strlen() on a NULL attribute name, terminating cupsd and disrupting all queues. A single crafted Print-Job request can trigger the crash when the client can reach the scheduler and s