CVE-2015-0204 - "Freak" attack - weak "EXPORT" grade keys


#1

Hello,

I have tested a few UCS with the standard self-produced cert using:

openssl s_client -connect your.UCS.TLD:443 -cipher EXPORT

And it seems like the “RSA-to-EXPORT_RSA downgrade” is possible even with the latest UCS PL 4.0-1. I know the impact is limited, given by the complexity needed for a successful attack. Still, I think the “EXPORT”-grade keys should be disabled asap.
Is this possible with a simple patch for UCS, or do we have to re-issue the certificate?

Best regards,
TP


#2

Hello,

this has been fixed on 01/13 with:
[ul]
[li]Univention Corporate Server 4.0 erratum 27[/li]
[li]Univention Corporate Server 3.2 erratum 272[/li][/ul]

We did not disable the RSA_EXPORT ciphers yet but fixed the actual exploit through which it is possible to force openssl to use/accept an weak export cipher even if it was not requested by the client.

Regards,
Janis Meybohm


#3

Hello,

that’s gread news! Again everything is fixed “automagically” with UCS.

Thanks and best regards,
TP