Jenkins 2.213 and earlier, LTS 2.204.1 and earlier improperly reuses encryption key parameters in the Inbound TCP Agent Protocol/3, allowing unauthorized attackers with knowledge of agent names to obtain the connection secrets for those agents, which can be used to connect to Jenkins, impersonating those agents.
https://jenkins.io/security/advisory/2020-01-29/#SECURITY-1682
https://access.redhat.com/errata/RHSA-2020:0683
https://access.redhat.com/errata/RHSA-2020:0681
https://access.redhat.com/errata/RHBA-2020:0675