Zephyr PTP Subsystem Bitwise Shift Vulnerability Leading to Undefined Behavior and Potential Denial-of-Service

A bitwise shift vulnerability has been identified in the Precision Time Protocol (PTP) subsystem of Zephyr, in versions through 4.3. This vulnerability allows remote attackers to cause undefined behavior and potentially crash the system. The issue arises when an attacker sends a crafted PTP_MSG_MANAGEMENT message that includes an unvalidated negative log_announce_interval value. This value is then used in a bitwise shift operation, where a sufficiently negative value can exceed the limits of a 64-bit integer, leading to undefined behavior in C. Such exploitation can cause a system crash on certain architectures or create logical errors by disrupting normal processing.

Impact

Exploitation of this vulnerability causes undefined behavior, which can lead to a system crash or logical errors. On some architectures, the kernel may crash due to an illegal instruction trap, while on others, it could calculate a zero timeout, causing resource starvation loops or other logical issues.

Reproduction

To reproduce this vulnerability, send a PTP_MSG_MANAGEMENT message with a negative log_announce_interval value, such as -127. This unvalidated value will be processed by the PTP subsystem, where it can cause a bitwise shift vulnerability by exceeding the 64-bit integer limit. The resulting undefined behavior can lead to a system crash or logical errors, depending on the architecture.

Remediation

The recommended fix is to validate the log_announce_interval and log_min_delay_req_interval values against the PTP specification limits upon receipt in the port_delay_resp_msg_process function.