[ASA-202006-2] gnutls: man-in-the-middle

[Morten Linderud]

Arch Linux Security Advisory ASA-202006-2
=========================================

Severity: High
Date    : 2020-06-06
CVE-ID  : CVE-2020-13777
Package : gnutls
Type    : man-in-the-middle
Remote  : Yes
Link    : https://security.archlinux.org/AVG-1177

Summary
=======

The package gnutls before version 3.6.14-1 is vulnerable to man-in-the-
middle.

Resolution
==========

Upgrade to 3.6.14-1.

# pacman -Syu "gnutls>=3.6.14-1"

The problem has been fixed upstream in version 3.6.14.

Workaround
==========

None.

Description
===========

GnuTLS 3.6.x before 3.6.14 uses incorrect cryptography for encrypting a
session ticket (a loss of confidentiality in TLS 1.2, and an
authentication bypass in TLS 1.3). The earliest affected version is
3.6.4 (2018-09-24) because of an error in a 2018-09-18 commit. Until
the first key rotation, the TLS server always uses wrong data in place
of an encryption key derived from an application.

Impact
======

A remote attacker can man-in-the-middle a connection to bypass
authentication in TLS 1.3, and recover previous conversations in TLS
1.2.

References
==========

https://gnutls.org/security-new.html#GNUTLS-SA-2020-06-03
https://gitlab.com/gnutls/gnutls/-/issues/1011
https://gitlab.com/gnutls/gnutls/-/commit/c2646aeee94e71cb15c90a3147cf3b5b0ca158ca?merge_request_iid=1275
https://security.archlinux.org/CVE-2020-13777
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