NetX Secure DTLS server issues predictable HelloVerifyRequest cookies, so a spoofed client can pass the return-routability check

In Eclipse ThreadX NetX Duo versions 6.0 through 6.5.2.202603a, the NetX Secure DTLS server fills HelloVerifyRequest cookies from NX_RAND(), by default the C library rand(), with no key and no binding to the client. An attacker who can predict the generator's output can pass the cookie exchange from a spoofed address and make the server send its handshake flight to a victim, using it as a traffic reflector.