CVE-2026-5072: ptp: Potential Denial of Service via PTP Interval Shift

A bitwise shift vulnerability in Zephyr's PTP subsystem allows a remote attacker to cause undefined behavior and potential system crashes. An attacker sends a crafted PTPMSGMANAGEMENT message to set an unvalidated negative logannounceinterval value in the port's data set. When a subsequent PTPMSGANNOUNCE message is processed, porttimersettimeoutrandom computes a timeout as NSECPERSEC >> -logseconds; if the attacker-supplied value is sufficiently negative (e.g., -127), the shift amount exceeds the 64-bit integer width, triggering undefined behavior in C. This can cause a system crash via a compiler-generated illegal instruction trap on some architectures, or produce an erroneous zero timeout leading to resource starvation loops or other logical errors.