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Date: Wed, 22 May 2013 15:24:59 +0300
From: Timo Sirainen <tss@....fi>
To: Jan Lieskovsky <jlieskov@...hat.com>
Cc: Agostino Sarubbo <ago@...too.org>,
 oss-security@...ts.openwall.com
Subject: Re: CVE request: dovecot : "APPEND" Parameters Processing Denial of Service Vulnerability

On 22.5.2013, at 15.17, Jan Lieskovsky <jlieskov@...hat.com> wrote:

> ----- Original Message -----
>> From: "Agostino Sarubbo" <ago@...too.org>
>> To: oss-security@...ts.openwall.com
>> Sent: Tuesday, May 21, 2013 8:58:04 PM
>> Subject: [oss-security] CVE request: dovecot : "APPEND" Parameters Processing Denial of Service Vulnerability
>> 
>> From the secunia advisory SA53492[1] :
>> 
>> Description
>> A vulnerability has been reported in Dovecot, which can be exploited by
>> malicious users to cause a DoS (Denial of Service).
>> 
>> The vulnerability is caused due to an error within IMAP functionality when
>> processing the "APPEND" parameters and can be exploited to cause a hang.
> 
> Timo, in relation with the previous (similar) one (thanks to Tomas Hoger for
> pointing out):
>  [1] http://thread.gmane.org/gmane.comp.security.oss.general/8916/focus=8934
>  [2] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=695138#15
> 
> this time the CVE identifier should be allocated / issue is valid, right?
> 
> While in the former [1], [2] case just the connection for the user issuing
> the command would crash, this time (assuming) either whole dovecot daemon
> might hang or even if the whole daemon wouldn't hang (and request is handled
> within a thread), that request would made the particular thread to consume
> excessive amount of CPU due to infinite loop, right?

A logged in user can cause his own IMAP connection process to eat 100% CPU, so it won't immediately hang other users. By default users can log in max. 10 times from the same IP, so attacker requires many IPs to cause a real DoS. And of course a valid user account, which means it will be immediately visible to admin who is causing the system to slow down.

> Timo, can you confirm / disprove a CVE identifier should be assigned to this?

I'm not against it, but I don't see this as that big of an issue, especially with v2.2 still not being widely used.

> Thank you && Regards, Jan.
> --
> Jan iankko Lieskovsky / Red Hat Security Response Team
> 
>> 
>> The vulnerability is reported in version 2.2.
>> 
>> 
>> Solution
>> Update to version 2.2.2.
>> 
>> Provided and/or discovered by
>> Reported by the vendor.
>> 
>> Original Advisory
>> http://www.dovecot.org/list/dovecot-news/2013-May/000255.html
>> 
>> Commit:
>> http://hg.dovecot.org/dovecot-2.2/rev/ea0390e1789f
>> 
>> [1]: https://secunia.com/advisories/53492/
>> 
>> --
>> Agostino Sarubbo
>> Gentoo Linux Developer
>> 
> 

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