KASAGO TCP/IP stack provided by Zuken Elmic generates ISNs(Initial Sequence Number) for TCP connections from an insufficiently random source. An attacker may be able to determine the ISN of the current or future TCP connections and either hijack existing ones or spoof future ones.

KASAGO TCP/IP stack provided by Zuken Elmic generates ISNs(Initial Sequence Number) for TCP connections from an insufficiently random source. An attacker may be able to determine the ISN of the current or future TCP connections and either hijack existing ones or spoof future ones.

Zuken Elmic KASAGO, TCP/IP protocol stack for embedded systems, uses its own random number generator function when generating TCP initial sequence numbers, which leads to use insufficient random values (CWE-330). Zuken Elmic reported this vulnerability to JPCERT/CC to notify users of its solution through JVN.