oss-security - Re: OpenDMARC signature bypass with multiple From addresses

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Message-ID: <20190917165453.GA17293@eldamar.local>
Date: Tue, 17 Sep 2019 18:54:53 +0200
From: Salvatore Bonaccorso <carnil@...ian.org>
To: oss-security@...ts.openwall.com
Subject: Re: OpenDMARC signature bypass with multiple From
 addresses

Hi,

On Wed, Sep 11, 2019 at 12:43:19PM +0200, Hanno Böck wrote:
> Hi,
> 
> Protonmail reported about a phishing incident in July:
> https://protonmail.com/blog/bellingcat-cyberattack-phishing/
> 
> This had this somewhat mysterious chapter:
> "Furthermore, the attackers attempted to exploit an unpatched
> vulnerability in an open source software that is widely used by email
> providers in an effort to bypass spam and abuse filters. We were
> previously aware of this vulnerability and have already been watching
> it for some time, but we will not disclose it here because the software
> in question is not developed by ProtonMail, and it has not yet been
> patched by the software maintainers. This vulnerability, however, is
> not widely known and indicates a higher level of sophistication on the
> part of the attackers."
> 
> After asking protonmail multiple times for a statement they answered
> and I learned that it's about this issue in OpenDMARC:
> https://github.com/trusteddomainproject/OpenDMARC/pull/48
> 
> It's an issue where by specifying multiple From addresses only one of
> them gets DMARC-checked.
> 
> There's no reaction from the OpenDMARC developers and it's unclear
> whether it's still actively developed. Given this is already actively
> exploited I think people should be aware of it and distros should
> probably apply the patch from the PR.

MITRE has assigned CVE-2019-16378 for this issue (requested via the
https://cveform.mitre.org/).

Regards,
Salvatore

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