Bug 458740 – <dev-libs/libxml2-2.9.1: Internal/external entity expansion (CVE-2013-0338, CVE-2013-0339)

• Status: RESOLVED FIXED
• Product: Gentoo Security

[Description Agostino Sarubbo 2013-02-22 13:58:08 UTC]

From ${URL} :

So here are the CVE's for the two big ones, libxml2 and expat. Both
are affected by the expansion of internal entities (which can be used
to consume resources) and external entities (which can cause a denial
of service against other services, be used to port scan, etc.).

To be clear:

====================
Internal entity expansion refers to the exponential/quadratic/fast
linear expansion of XML entities, e.g.:
====================
<!DOCTYPE xmlbomb [
<!ENTITY a "1234567890" >
<!ENTITY b "&a;&a;&a;&a;&a;&a;&a;&a;">
<!ENTITY c "&b;&b;&b;&b;&b;&b;&b;&b;">
<!ENTITY d "&c;&c;&c;&c;&c;&c;&c;&c;">
]>
<bomb>&d;</bomb>

or

<!DOCTYPE bomb [
<!ENTITY a "xxxxxxx... a couple of ten thousand chars">
]>
<bomb>&a;&a;&a;... repeat</bomb>

Which causes resources to be consumed



====================
External entity expansion refers to the loading of external resources
such as XML entities from another server or a local file:
====================
<!DOCTYPE external [
<!ENTITY ee SYSTEM "http://www.example.org/some.xml">
]>
<root>&ee;</root>


<!DOCTYPE external [
<!ENTITY ee SYSTEM "file:///PATH/TO/simple.xml">
]>
<root>&ee;</root>

Which can cause resources to be consumed or can result in port
scanning /application scanning information being sent to the attacker.


So the CVE's to use:

Please use CVE-2013-0338 for libxml2 internal entity expansion

Please use CVE-2013-0339 for libxml2 external entities expansion

[Comment 1 Alexandre Rostovtsev (RETIRED) 2013-02-26 05:13:30 UTC]

Isn't this a duplicate of bug #458430?

[Comment 2 GLSAMaker/CVETool Bot 2013-04-26 11:09:17 UTC]

CVE-2013-0338 (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2013-0338):
  libxml2 2.9.0 and earlier allows context-dependent attackers to cause a
  denial of service (CPU and memory consumption) via an XML file containing an
  entity declaration with long replacement text and many references to this
  entity, aka "internal entity expansion" with linear complexity.

[Comment 3 Chris Reffett (RETIRED) 2013-07-07 17:02:39 UTC]

Both fixed [1] in libxml2-2.9.1.

[1] https://git.gnome.org/browse/libxml2/commit/?id=23f05e0c33987d6605387b300c4be5da2120a7ab

[Comment 4 Alexandre Rostovtsev (RETIRED) 2013-07-12 17:57:18 UTC]

>=libxml2-2.9.1 is being stabilized at bug #476438

[Comment 5 Sergey Popov 2013-08-28 07:36:38 UTC]

Added to existing GLSA draft

[Comment 6 GLSAMaker/CVETool Bot 2013-11-10 15:19:03 UTC]

This issue was resolved and addressed in
 GLSA 201311-06 at http://security.gentoo.org/glsa/glsa-201311-06.xml
by GLSA coordinator Sean Amoss (ackle).