firefox and thunderbird is vulnerable to arbitrary code execution attacks. The vulnerability exists as the name_parse function in evdns.c in libevent before 2.1.6-beta allows remote attackers to have unspecified impact via vectors involving the label_len variable, which triggers an out-of-bounds stack read.
www.debian.org/security/2017/dsa-3789
www.openwall.com/lists/oss-security/2017/01/31/17
www.openwall.com/lists/oss-security/2017/02/02/7
www.securityfocus.com/bid/96014
www.securitytracker.com/id/1038320
access.redhat.com/errata/RHSA-2017:1104
access.redhat.com/errata/RHSA-2017:1106
access.redhat.com/errata/RHSA-2017:1201
access.redhat.com/security/cve/CVE-2016-10195
access.redhat.com/security/cve/CVE-2016-10196
access.redhat.com/security/cve/CVE-2016-10197
access.redhat.com/security/updates/classification/#critical
bugzilla.redhat.com/show_bug.cgi?id=1443326
github.com/libevent/libevent/blob/release-2.1.6-beta/ChangeLog
github.com/libevent/libevent/commit/96f64a022014a208105ead6c8a7066018449d86d
github.com/libevent/libevent/issues/317
security.gentoo.org/glsa/201705-01
www.mozilla.org/en-US/security/advisories/mfsa2017-08