Bug 1000109 (CVE-2013-0340)

Summary: CVE-2013-0340 expat: internal entity expansion
Product: [Other] Security Response Reporter: Vincent Danen <vdanen>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED WONTFIX QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: erik-fedora, jkurik, jorton, rjones
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2013-08-28 09:58:51 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Bug Depends On:    
Bug Blocks: 1000112    

Description Vincent Danen 2013-08-22 17:30:50 UTC
As reported on oss-security [1]:

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

...
Please use CVE-2013-0340 for expat internal entity expansion


[1] http://www.openwall.com/lists/oss-security/2013/02/22/4

Comment 1 Huzaifa S. Sidhpurwala 2013-08-28 09:58:51 UTC
Applications linked with expat can mitigate this issue, by calling the XML_SetEntityDeclHandler() function with the name of an alternative function that can handle entities more safely.

Since API levels mitigations are in place, closing this as wontfix.