Ssl.com: DCV bypass and issue fake certificates for any MX hostname

#1

Post by xPaw » Sat, Apr 19, 2025, 6:44 PM UTC

Ssl.com: DCV bypass and issue fake certificates for any MX hostname
bugzilla.mozilla.org

Re: Ssl.com: DCV bypass and issue fake certificates for any MX hostname

#2

Post by cmeacham98 » Sat, Apr 19, 2025, 7:14 PM UTC

This is a ... pretty serious oversight.

But at least it initially appears SSL.com is taking it seriously, we'll have to see what the report says.

Re: Ssl.com: DCV bypass and issue fake certificates for any MX hostname

#3

Post by CrimsonRain » Sat, Apr 19, 2025, 7:19 PM UTC

I guess they can check logs and find how many times this has been abused already? Can we trust them to release full transparent report?

Re: Ssl.com: DCV bypass and issue fake certificates for any MX hostname

#4

Post by thayne » Sat, Apr 19, 2025, 7:20 PM UTC

CrimsonRain wrote: post #3

I guess they can check logs and find how many times this has been abused already? Can we trust them to release full transparent report?

All such certs should be in transparancy logs, so I think it should be possible for a third party to verify.

Re: Ssl.com: DCV bypass and issue fake certificates for any MX hostname

#5

Post by thayne » Sat, Apr 19, 2025, 7:22 PM UTC

Have they started revoking invalid certs?

Re: Ssl.com: DCV bypass and issue fake certificates for any MX hostname

#6

Post by 0x0 » Sat, Apr 19, 2025, 7:23 PM UTC

So I guess you couldn't get certificates for any random (MX) domain, only for those where you can obtain an inbox / user account. Still really bad, especially for things like gmail.com, but also larger enterprises. Intense.

Re: Ssl.com: DCV bypass and issue fake certificates for any MX hostname

#7

Post by tptacek » Sat, Apr 19, 2025, 7:28 PM UTC

0x0 wrote: post #6

So I guess you couldn't get certificates for any random (MX) domain, only for those where you can obtain an inbox / user account. Still really bad, especially for things like gmail.com, but also larger enterprises. Intense.

It is unlikely that SSL.com would issue a certificate for any major mail host; it would be malpractice for them not to have some kind of exclusion list.

Issuing a Google certificate is a good way to get your whole CA killed.

Re: Ssl.com: DCV bypass and issue fake certificates for any MX hostname

#8

Post by mukesh610 » Sat, Apr 19, 2025, 7:29 PM UTC

0x0 wrote: post #6

So I guess you couldn't get certificates for any random (MX) domain, only for those where you can obtain an inbox / user account. Still really bad, especially for things like gmail.com, but also larger enterprises. Intense.

Even then, use of a DNS CAA record should mitigate this, right?

Re: Ssl.com: DCV bypass and issue fake certificates for any MX hostname

#9

Post by voxic11 » Sat, Apr 19, 2025, 7:30 PM UTC

thayne wrote: post #5

Have they started revoking invalid certs?

You can see the cert was revoked here https://crt.sh/?id=17926238129

Re: Ssl.com: DCV bypass and issue fake certificates for any MX hostname

#10

Post by jsheard » Sat, Apr 19, 2025, 7:34 PM UTC

mukesh610 wrote: post #8

0x0 wrote: post #6

So I guess you couldn't get certificates for any random (MX) domain, only for those where you can obtain an inbox / user account. Still really bad, especially for things like gmail.com, but also larger enterprises. Intense.

Even then, use of a DNS CAA record should mitigate this, right?

Yeah - unless you're an actual SSL.com customer, in which case your CAA records would allow it. That's a much smaller blast radius at least.