VMWare Zimbra Mailer | DKIM longterm Mail Replay vulnerability Jan 30 2016 11:13AM
t schughart prosec-networks com

VMWare Zimbra Mailer Release 8.6.0.GA, latest patch and prior versions
with DKIM implementation are vulnerable to longterm Mail Replay attacks.

If the expiration header is not set, the signature never expires. This
means, that the e-mail, perhaps catched while performing a man in the
middle attack, can be replayed years after catching it.

This can be combined with the spoofed reply-to header field, because the
header field is not hashed by Zimbras DKIM implementation.

Supporter of vulnerability analysis: Steffen Mauer @this point I want to
thank Steffen for his good work =)

To configure DKIM with VMware Zimbra the official documentation advises
the administrator to use the zimbra management tools. With the
management tools there is no possibility to add custom Headerâ??s for
hashing it with DKIM or for setting the expiration DKIM Header.

PoC Headerpart:
The DKIM Implementation implements the following DKIM Header:
Dkim-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=0mail.org;
s=76820800-C732-11E5-858E-A0DD11F66BE4; t=1454147943;
Report Timeline:

There has been no response from VMware for 14 Days.

Best regards / Mit freundlichen Grü�en

Tim Schughart
IT Security engineer

ProSec Networks
Website: https://www.prosec-networks.com
E-Mail: info (at) prosec.networks (dot) com [email concealed]
Phone: +49(0) 2621 9469 252

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