bugtraq - Re: Exploiting Google MX servers as Open SMTP Relays

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Pine.LNX.4.62.0805072131580.693@linuxbox.org>
Date: Wed, 7 May 2008 21:32:32 -0500 (CDT)
From: Gadi Evron <ge@...uxbox.org>
To: pablo.ximenes@....edu
Cc: bugtraq@...urityfocus.com
Subject: Re: Exploiting Google MX servers as Open SMTP Relays

On Wed, 7 May 2008 pablo.ximenes@....edu wrote:
>
> Vulnerability Report:
>
> As part of our recent work on the trust hierarchy that exists among email providers throughout the Internet, we have uncovered a serious security flaw in Ggoogle's free email service, Gmail. This vulnerability exposes Google's email servers in a way that allows an attacker to use them as open spam and phishing relays. This issue is related to the risk of a malicious user abusing Gmail's email forwarding functionality. This is possible because Gmail's email forwarding functionality does not impose proper security restrictions during its setup process and can be easily subverted. By exploiting this problem an attacker can send unlimited spam and phishing (i.e. forged) email messages that are delivered by Google's very own SMTP servers. Since the messages are delivered by Google's own servers, an attack based on this flaw is able to bypass all spam filters that are based on the blacklist / whitelist concept. We were able to confirm that this vulnerability is indeed exploitable b
> y crafting a proof of concept attack that allowed us to send any number of forged email messages without restriction through Google's server infrastructure. We have also verified that this flaw allows attackers to bypass spam filters by using our method to send messages that are usually flagged as spam. While sending these messages directly from our network in the traditional way had the messages classified as spam, by sending the very same messages using our exploit, the messages were delivered directly to the victim's inbox, thus bypassing filters.
>
> Impact:
>
> All email providers that offer Google's SMTP servers any special level of trust (e.g. whitelist status) are vulnerable.

A lot of spam is currently being sent that way.

 	Gadi.


> Disclosure:
> We have contacted Google about this issue and are waiting for their position before releasing further details.
>
> For more information, visit our homepage:
> http://ece.uprm.edu/~andre/insert
>
>
> Regards,
>
>
> Pablo Ximenes, André dos Santos
>
> INSERT - Information Security Research Team
> University of PR at Mayaguez (UPRM), USA
> State University of Ceará (UECE), Brazil
>
> pablo.ximenes@....edu, andre@...santos.org
>