SOGo 2.x before 2.4.1 and 3.x through 5.x before 5.1.1 does not validate the signatures of any SAML assertions it receives. Any actor with network access to the deployment could impersonate users when SAML is the authentication method. (Only versions after 2.0.5a are affected.)
https://www.debian.org/security/2021/dsa-5029
https://lists.debian.org/debian-lts-announce/2021/07/msg00007.html
https://github.com/inverse-inc/sogo/blob/master/CHANGELOG.md