It looks like the referenced vulnerability is CVE-2019-10149.

It was first seen in version 4.87, and patched in version 4.93.

Latest Exim is 4.94

The US and Canada have similar populations, are geographically close, and have similar testing rates.

Blacks/African Americans, Hispanics, and Native Americans count for 30% of US population; they count for less than 10% in Canada. These groups have infection rates 4 to 5 times higher than non-Hispanic whites. That's similar?

US has tested 52,942,145 out of 328,239,523 (~16%). Canada has tested 98361 per million people (~10%). A 60% difference in test rates is similar?

For all the US-bashers / Europe-lovers, let's take a look at some numbers from Worldometers https://www.worldometers.info/coronavirus/:

Country Total Cases Total Deaths Total Tests Population
USA 4170328 147341 51553663 331124024
Brazil 2289951 84207 4911063 212652984
Spain 317246 28429 6320836 46755958
UK 297146 45554 13974097 67908416
Italy 245338 35092 6415041 60455955
Germany 205142 9187 7418812 83801039
France 179398 30182 2982302 65282797
Canada 112672 8874 3697322 37762377

Looks bad for the US and Brazil, doesn't it? However, if we normalize the data:

Country Tot Cases/1M pop Deaths/1M pop Tests/1M pop Deaths/Case %
USA 12594 445 155693 3.5331
Brazil 10768 396 23094 3.6772
Spain 6785 608 135188 8.9612
UK 4376 671 205779 15.3305
Italy 4058 580 106111 14.3035
Germany 2448 110 88529 4.4784
France 2748 462 45683 16.8240
Canada 2984 235 97910 7.8760

Looks like if you want to avoid infection, Europe's the place to be, but if you want to survive after getting infected, then get to the US. (Deaths per Infection is the number to look at; lower is better.) Testing rate is better, too - except for UK; probably easier to test small island than large country.

Also, the Mayo Clinic https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/herd-immunity-and-coronavirus/art-20486808 estimates the US needs 70% recovered or vaccinated to achieve herd immunity. Assuming that holds true for other countries, looks like the US has the best progress on that, as well. (Total cases per 1 M population; higher is better)

After all, they offered an official apology to the Navajo nation after they "defiled" the moon with the ashes of Eugene Shoemaker back in '98. And promised not to do something similar without "consultation" (aka permission).