CVE-2020-13777
gnutls: session resumption works without master key allowing MITM
Severity
ImportantRed Hat Product Security
CVSS 3.1
Review impact separately from score.
Published · June 3, 2020
Updated · October 14, 2026
Description
A flaw was found in GnuTLS, in versions starting from 3.6.4, where it does not session the ticket encryption key in a secure fashion by the application which is connecting. This flaw allows an attacker to craft a man-in-the-middle-attack, with the ability to bypass the TLS1.3 authentication and also recover older conversations when TLS1.2 is in use. The highest threat to this flaw is to confidentiality and integrity.
Statement
GnuTLS versions as shipped with Red Hat Enterprise Linux 7 and earlier are not affected, as the bug was introduced in upstream at GnuTLS version 3.6.4. The older versions do not carry the affected code.
CVSS score applicability
The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.
Mitigation
There's no available mitigation for this issue.
CVSS / CWE
CVSS 3.1 · 7.4CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
CWE-345 · Insufficient Verification of Data Authenticity