CVE-2013-0340

Published: 21 January 2014

expat 2.1.0 and earlier does not properly handle entities expansion unless an application developer uses the XML_SetEntityDeclHandler function, which allows remote attackers to cause a denial of service (resource consumption), send HTTP requests to intranet servers, or read arbitrary files via a crafted XML document, aka an XML External Entity (XXE) issue. NOTE: it could be argued that because expat already provides the ability to disable external entity expansion, the responsibility for resolving this issue lies with application developers; according to this argument, this entry should be REJECTed, and each affected application would need its own CVE.

Notes

PoC in oss-sec
no upstream commits as of 2013-03-21. Contacted upstream on their
(possibly moderated) expat-bugs mailing list since their bug tracker was
down
still no commits or upstream comments as of 2013-04-23

Expat does not read or parse external entities directly, it is
up to applications to do so.
http://seclists.org/oss-sec/2013/q2/78
marking as ignored, application-specific CVEs should be assigned
to individual applications.

upstream libexpat has introduced heuristics in 2.4.0 to limit
the damage due to various entity expansion issues. These fixes won't be
backported to previous releases due to the risk of regression due to the
size, complexity, and new APIs.

Status

References

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-0340
• http://www.openwall.com/lists/oss-security/2013/02/22/3
• http://mail.libexpat.org/pipermail/expat-bugs/2013-March/thread.html
• https://github.com/libexpat/libexpat/blob/R_2_4_0/expat/Changes
• NVD
• Launchpad
• Debian

Bugs

• https://bugs.launchpad.net/ubuntu/+source/expat/+bug/1943133