A gnutls28 security update has been released for Debian GNU/Linux 10 to address a flaw was reported in the TLS session ticket key construction in GnuTLS.

DSA 4697-1: gnutls28 security update

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Debian Security Advisory DSA-4697-1 security@debian.org
  https://www.debian.org/security/ Salvatore Bonaccorso
June 06, 2020   https://www.debian.org/security/faq
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Package : gnutls28
CVE ID : CVE-2020-13777
Debian Bug : 962289

A flaw was reported in the TLS session ticket key construction in
GnuTLS, a library implementing the TLS and SSL protocols. The flaw
caused the TLS server to not securely construct a session ticket
encryption key considering the application supplied secret, allowing a
man-in-the-middle attacker to bypass authentication in TLS 1.3 and
recover previous conversations in TLS 1.2.

For the stable distribution (buster), this problem has been fixed in
version 3.6.7-4+deb10u4.

We recommend that you upgrade your gnutls28 packages.

For the detailed security status of gnutls28 please refer to its
security tracker page at:
  https://security-tracker.debian.org/tracker/gnutls28

Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at:   https://www.debian.org/security/