oss-security - Re: CVE Request: libxml2 external parsed entities issue

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Date: Mon, 28 Oct 2013 19:17:51 +0100
From: Nicolas Grégoire <nicolas.gregoire@...rri.fr>
To: oss-security@...ts.openwall.com
Subject: Re: CVE Request: libxml2 external parsed entities
 issue

>>libxml2 earlier than 2.9.0 fetches external parsed entities by
>>default, with no way to disable the behaviour.
>>
>>Fixed by the following commit:
>>https://git.gnome.org/browse/libxml2/commit/?id=4629ee02ac649c27f9c0cf98ba017c6b5526070f 

[...]

> Hrm, I would have thought CVE-2013-0339 was for the entities expansion DoS issue
> fixed by this commit:
> 
> https://git.gnome.org/browse/libxml2/commit/?id=23f05e0c33987d6605387b300c4be5da2120a7ab
> 
> The other one is for external entities expansion being enabled by default with
> no way to turn it off. You would lump them together?

It's still unclear to me what exactly CVE-2013-0339 covers.

Patch for the entity expansion DoS:
https://git.gnome.org/browse/libxml2/commit/?id=23f05e0c33987d6605387b300c4be5da2120a7ab

Patch for not expanding external entities by default:
https://git.gnome.org/browse/libxml2/commit/?id=4629ee02ac649c27f9c0cf98ba017c6b5526070f

Are both patches covered? The second one is quite important as it kills
the classic XXE vector <!ENTITY foo SYSTEM "/etc/passwd">

For Ubuntu, CVE-2013-0339 covers the XXE attack.
https://bugs.launchpad.net/ubuntu/%2Bsource/libxml2/%2Bbug/1194410

For Debian, it's "large memory consumption" only:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=702260

For RedHat, it covers both but "libxml2 already provides mechanisms to
disable external entities which applications can use. Closing this flaw
as 'wontfix'": https://bugzilla.redhat.com/show_bug.cgi?id=915149

And the official page for the CVE isn't helpful:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-0339

Regards,
Nicolas Grégoire

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