Bug 1379553 (CVE-2016-9180)

Summary:	CVE-2016-9180 perl-XML-Twig: expand_external_ents option fails to work as documented
Product:	[Other] Security Response	Reporter:	Doran Moppert <dmoppert>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED WONTFIX	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	carnil, cweyl, jplesnik, perl-devel, perl-maint-list, ppisar, psabata, sardella
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:	A vulnerability was found in perl-XML-Twig. External entity expansion (XXE) took place regardless of the setting 'expand_external_ents', which was supposed to disable this functionality if set to 0 (the default) or -1. An attacker could craft an XML message which, when processed by an application using perl-XML-Twig, could cause denial of service or, potentially, information disclosure.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2016-11-17 02:47:08 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1379554
Bug Blocks:	1377998

Description Doran Moppert 2016-09-27 06:49:56 UTC

The option to `expand_external_ents`, documented as controlling external entity
expansion in XML::Twig does not work.  External entities are always expanded,
regardless of the option's setting.

Upstream bug:

https://rt.cpan.org/Public/Bug/Display.html?id=118097

Comment 1 Doran Moppert 2016-09-27 06:52:24 UTC

Created perl-XML-Twig tracking bugs for this issue:

Affects: fedora-all [bug 1379554]

Comment 2 Doran Moppert 2016-11-17 01:34:02 UTC

Statement:

Red Hat Product Security has rated this issue as having Moderate security
impact. This issue is not currently planned to be addressed in future
updates. For additional information, refer to the Issue Severity
Classification: https://access.redhat.com/security/updates/classification/.

Comment 3 Doran Moppert 2016-11-17 01:34:09 UTC

Acknowledgments:

Name: Doran Moppert (Red Hat Product Security Team)

Comment 4 Petr Pisar 2017-07-26 14:20:32 UTC

Upstream released 3.50 that added no_xxe flag that implements the desired behavior, but expand_external_ents flag, subject of this vulnerability, still has no effect.

So while XML-Twig >= 3.50 can now be used safely, the reported bug still exists.