The URL pattern of "" (the empty string) which exactly maps to the context root was not correctly handled in Apache Tomcat 9.0.0.M1 to 9.0.4, 8.5.0 to 8.5.27, 8.0.0.RC1 to 8.0.49 and 7.0.0 to 7.0.84 when used as part of a security constraint definition. This caused the constraint to be ignored. It was, therefore, possible for unauthorised users to gain access to web application resources that should have been protected. Only security constraints with a URL pattern of the empty string were affected.
https://www.oracle.com/technetwork/security-advisory/cpujul2019-5072835.html
https://www.oracle.com/technetwork/security-advisory/cpuapr2019-5072813.html
https://www.oracle.com/security-alerts/cpuapr2020.html
https://www.debian.org/security/2018/dsa-4281
https://usn.ubuntu.com/3665-1/
https://security.netapp.com/advisory/ntap-20180706-0001/
https://lists.debian.org/debian-lts-announce/2018/07/msg00044.html
https://lists.debian.org/debian-lts-announce/2018/06/msg00008.html
https://lists.debian.org/debian-lts-announce/2018/03/msg00004.html
https://access.redhat.com/errata/RHSA-2019:2205
https://access.redhat.com/errata/RHSA-2018:2939
https://access.redhat.com/errata/RHSA-2018:1451
https://access.redhat.com/errata/RHSA-2018:1450
https://access.redhat.com/errata/RHSA-2018:1449
https://access.redhat.com/errata/RHSA-2018:1448
https://access.redhat.com/errata/RHSA-2018:1447
https://access.redhat.com/errata/RHSA-2018:1320
https://access.redhat.com/errata/RHSA-2018:0466
https://access.redhat.com/errata/RHSA-2018:0465
http://www.securitytracker.com/id/1040427
http://www.securityfocus.com/bid/103170
http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html
http://www.oracle.com/technetwork/security-advisory/cpujul2018-4258247.html