Memory safety bugs were reported in Firefox 54, Firefox ESR 52.2, and Thunderbird 52.2. Some of these bugs showed evidence of memory corruption and we presume that with enough effort that some of these could be exploited to run arbitrary code. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.
http://www.securityfocus.com/bid/100201
http://www.securitytracker.com/id/1039124
https://access.redhat.com/errata/RHSA-2017:2456
https://access.redhat.com/errata/RHSA-2017:2534
https://security.gentoo.org/glsa/201803-14
https://www.debian.org/security/2017/dsa-3928
https://www.debian.org/security/2017/dsa-3968
https://www.mozilla.org/security/advisories/mfsa2017-18/
Source: MITRE
Published: 2018-06-11
Updated: 2018-08-01
Type: CWE-119
Base Score: 10
Vector: AV:N/AC:L/Au:N/C:C/I:C/A:C
Impact Score: 10
Exploitability Score: 10
Severity: HIGH
Base Score: 9.8
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Impact Score: 5.9
Exploitability Score: 3.9
Severity: CRITICAL