WEBrick::HTTPAuth::DigestAuth in Ruby through 2.4.7, 2.5.x through 2.5.6, and 2.6.x through 2.6.4 has a regular expression Denial of Service cause by looping/backtracking. A victim must expose a WEBrick server that uses DigestAuth to the Internet or a untrusted network.
lists.opensuse.org/opensuse-security-announce/2020-03/msg00041.html
hackerone.com/reports/661722
lists.debian.org/debian-lts-announce/2019/11/msg00025.html
lists.debian.org/debian-lts-announce/2019/12/msg00009.html
lists.debian.org/debian-lts-announce/2020/08/msg00027.html
lists.debian.org/debian-lts-announce/2023/04/msg00033.html
seclists.org/bugtraq/2019/Dec/31
seclists.org/bugtraq/2019/Dec/32
security.gentoo.org/glsa/202003-06
www.debian.org/security/2019/dsa-4587
www.oracle.com/security-alerts/cpujan2020.html