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.
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.
Created perl-XML-Twig tracking bugs for this issue:
Affects: fedora-all [bug 1379554]
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
Name: Doran Moppert (Red Hat Product Security Team)
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.