---
id: CVE-2020-13777
title: >-
  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)
summary: >-
  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 err…
severity: high
cvss: 7.4
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-327
vendor: gnu
product: gnutls
affected:
  - 'gnutls >= 3.6.0, < 3.6.14'
  - fedora = 31
  - fedora = 32
  - ubuntu_linux = 19.10
  - ubuntu_linux = 20.04
  - debian_linux = 10.0
patched:
  - gnutls 3.6.14
published: '2020-06-04'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T10:17:29.130'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2020-13777'
references:
  - url: 'http://lists.opensuse.org/opensuse-security-announce/2020-06/msg00015.html'
    label: cve@mitre.org
  - url: 'https://gnutls.org/security-new.html#GNUTLS-SA-2020-06-03'
    label: cve@mitre.org
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6C4DHUKV6M6SJ5CV6KVHZNHNF7HCUE5P/
    label: cve@mitre.org
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6RTXZOXC4MHTFE2HKY6IAZMF2WHD2WMV/
    label: cve@mitre.org
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RRQBFK3UZ7SV76IYDTS4PS6ABS2DSJHK/
    label: cve@mitre.org
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VMB3UGI5H5RCFRU6OGRPMNUCNLJGEN7Y/
    label: cve@mitre.org
  - url: 'https://security.gentoo.org/glsa/202006-01'
    label: cve@mitre.org
  - url: 'https://security.netapp.com/advisory/ntap-20200619-0004/'
    label: cve@mitre.org
  - url: 'https://usn.ubuntu.com/4384-1/'
    label: cve@mitre.org
  - url: 'https://www.debian.org/security/2020/dsa-4697'
    label: cve@mitre.org
  - url: 'http://lists.opensuse.org/opensuse-security-announce/2020-06/msg00015.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://gnutls.org/security-new.html#GNUTLS-SA-2020-06-03'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6C4DHUKV6M6SJ5CV6KVHZNHNF7HCUE5P/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6RTXZOXC4MHTFE2HKY6IAZMF2WHD2WMV/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RRQBFK3UZ7SV76IYDTS4PS6ABS2DSJHK/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VMB3UGI5H5RCFRU6OGRPMNUCNLJGEN7Y/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security.gentoo.org/glsa/202006-01'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security.netapp.com/advisory/ntap-20200619-0004/'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://usn.ubuntu.com/4384-1/'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://www.debian.org/security/2020/dsa-4697'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-398330.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - exploit-available
  - cve.org
epss: 0.22284
epssPercentile: 0.97641
exploits:
  github: 3
  githubRepos:
    - 'https://github.com/0xxon/cve-2020-13777'
    - 'https://github.com/shigeki/challenge_CVE-2020-13777'
    - 'https://github.com/prprhyt/PoC_TLS1_3_CVE-2020-13777'
  checkedAt: '2026-10-14T10:26:15.308Z'
exploitAvailable: true
ingestedAt: '2026-10-14T10:25:41.176Z'
---

## Overview

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.

## Affected

- `gnutls >= 3.6.0, < 3.6.14`
- `fedora = 31`
- `fedora = 32`
- `ubuntu_linux = 19.10`
- `ubuntu_linux = 20.04`
- `debian_linux = 10.0`

## Remediation

Upgrade past the affected range:

- `gnutls 3.6.14`