Security constraints defined by annotations of Servlets 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 were only applied once a Servlet had been loaded. Because security constraints defined in this way apply to the URL pattern and any URLs below that point, it was possible - depending on the order Servlets were loaded - for some security constraints not to be applied. This could have exposed resources to users who were not authorised to access them.
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-2018:1320
https://access.redhat.com/errata/RHSA-2018:0466
https://access.redhat.com/errata/RHSA-2018:0465
http://www.securitytracker.com/id/1040428
http://www.securityfocus.com/bid/103144
http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html
http://www.oracle.com/technetwork/security-advisory/cpujul2018-4258247.html