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Date: Wed, 03 Jul 2013 21:37:11 -0600
From: Kurt Seifried <kseifried@...hat.com>
To: oss-security@...ts.openwall.com
CC: Michael Tokarev <mjt@....msk.ru>, Michael Jerris <mike@...ris.com>,
        Ken Rice <krice@...eswitch.org>
Subject: Re: CVE request: FreeSWITCH regex substitution 3 buffer
 overflows

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On 07/01/2013 02:46 PM, Michael Tokarev wrote:
> Hello.
> 
> Yesterday I started thinking for the first time about some VOIP 
> solution for our office, and come across FreeSWITCH software -- 
> www.freeswitch.org.  After talking on IRC a bit, I decided to take
> a look at the source, because a question asked by one of the users
> looked interesting to me.
> 
> And immediately I discovered 3 buffer overflows in the _first_ 
> function I ever saw in the source of this software.
> 
> http://jira.freeswitch.org/browse/FS-5566 - it is the original 
> bugreport which looked innocent enough initially.
> 
> http://jira.freeswitch.org/secure/attachment/18855/0001-regex_subst-allow-n-in-regex-substitutions-and-fix-3.patch
> -- this is a patch of mine that fixes initial bug and also 3 buffer
> overflows I found when dealing with the issue.
> 
> Some context.  FreeSWITCH's routing mechanism is based almost 
> entirely on regular expressions and uses substring matches in the
> core routing (dialplan).  So the regexps are matched against
> untrusted input (which is especially mentioned in the docs).  But
> ofcourse users aren't easy with writing regexps correctly, always
> constraining the length of the input properly.
> 
> So, if there are any references to unconstrained input in any
> dialplan expressions -- that is, instead of \d{10}, \d+ is used,
> we're getting a remotely triggerable buffer overflows with good
> potential of remote code execution.
> 
> As simple as that.
> 
> It _looks_ like the default configuration isn't affected since
> apparently all regexes there are constrained.  But we can't be sure
> for all user configs.
> 
> I haven't studied actual potential for code execution, but from a
> quick view it appears quite possible.
> 
> Thanks,
> 
> /mjt

Same researcher/version/vuln type so CVE MERGE. Please use
CVE-2013-2238 for this issue.



- -- 
Kurt Seifried Red Hat Security Response Team (SRT)
PGP: 0x5E267993 A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993
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