GnuTLS 3.6.x before 3.6.13 uses incorrect cryptography for DTLS. The earliest affected version is 3.6.3 (2018-07-16) because of an error in a 2017-10-06 commit. The DTLS client always uses 32 '\0' bytes instead of a random value, and thus contributes no randomness to a DTLS negotiation. This breaks the security guarantees of the DTLS protocol.
https://www.gnutls.org/security-new.html#GNUTLS-SA-2020-03-31
https://www.debian.org/security/2020/dsa-4652
https://usn.ubuntu.com/4322-1/
https://security.netapp.com/advisory/ntap-20200416-0002/
https://security.gentoo.org/glsa/202004-06
https://gitlab.com/gnutls/gnutls/-/issues/960
https://gitlab.com/gnutls/gnutls/-/commit/5b595e8e52653f6c5726a4cdd8fddeb6e83804d2
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00015.html