Iran has been on the sanctioned blacklist for Cisco (and other enterprise level tech in government use) sales for decades. The only way Iran could get the gear into the country is by using unauthorized channels. Knowing there were no authorized sales, this would be very easy way for state level espionage organization to build compromised devices to flow into Iran.

If you buy a stolen computer, and there is a virus on it, you don’t really have any claim against the computer manufacturer.