Bug 1000109 (CVE-2013-0340) - CVE-2013-0340 expat: internal entity expansion
Summary: CVE-2013-0340 expat: internal entity expansion
Alias: CVE-2013-0340
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
Depends On:
Blocks: 1000112
TreeView+ depends on / blocked
Reported: 2013-08-22 17:30 UTC by Vincent Danen
Modified: 2019-09-29 13:07 UTC (History)
4 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2013-08-28 09:58:51 UTC

Attachments (Terms of Use)

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;">


<!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.

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