SOGo is using insecure signature validation. It 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.
blogs.akamai.com/2021/06/sogo-and-packetfence-impacted-by-saml-implementation-vulnerabilities.html
github.com/inverse-inc/sogo/blob/master/CHANGELOG.md
lists.debian.org/debian-lts-announce/2021/07/msg00007.html
security-tracker.debian.org/tracker/CVE-2021-33054
www.debian.org/security/2021/dsa-5029
www.sogo.nu/news.html