---
id: CVE-2020-24659
title: An issue was discovered in GnuTLS before 3.6.15
summary: >-
  An issue was discovered in GnuTLS before 3.6.15. A server can trigger a NULL
  pointer dereference in a TLS 1.3 client if a no_renegotiation alert is sent
  with unexpected timing, and then an invalid second handshake occurs. The crash
  happe…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-476
  - CWE-787
vendor: gnu
product: gnutls
affected:
  - gnutls < 3.6.15
  - fedora = 32
  - fedora = 33
  - leap = 15.1
  - leap = 15.2
  - ubuntu_linux = 20.04
patched:
  - gnutls 3.6.15
published: '2020-09-04'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T10:17:32.493'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2020-24659'
references:
  - url: 'http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00054.html'
    label: cve@mitre.org
  - url: 'http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00060.html'
    label: cve@mitre.org
  - url: 'https://gitlab.com/gnutls/gnutls/-/issues/1071'
    label: cve@mitre.org
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/62BUAI4FQQLG6VTKRT7SUZPGJJ4NASQ3/
    label: cve@mitre.org
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AWN56FDLQQXT2D2YHNI4TYH432TDMQ7N/
    label: cve@mitre.org
  - url: 'https://security.gentoo.org/glsa/202009-01'
    label: cve@mitre.org
  - url: 'https://security.netapp.com/advisory/ntap-20200911-0006/'
    label: cve@mitre.org
  - url: 'https://usn.ubuntu.com/4491-1/'
    label: cve@mitre.org
  - url: 'https://www.gnutls.org/security-new.html#GNUTLS-SA-2020-09-04'
    label: cve@mitre.org
  - url: 'http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00054.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00060.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://gitlab.com/gnutls/gnutls/-/issues/1071'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/62BUAI4FQQLG6VTKRT7SUZPGJJ4NASQ3/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AWN56FDLQQXT2D2YHNI4TYH432TDMQ7N/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security.gentoo.org/glsa/202009-01'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security.netapp.com/advisory/ntap-20200911-0006/'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://usn.ubuntu.com/4491-1/'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://www.gnutls.org/security-new.html#GNUTLS-SA-2020-09-04'
    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
epss: 0.0373
epssPercentile: 0.8959
ingestedAt: '2026-10-14T10:25:41.180Z'
---

## Overview

An issue was discovered in GnuTLS before 3.6.15. A server can trigger a NULL pointer dereference in a TLS 1.3 client if a no_renegotiation alert is sent with unexpected timing, and then an invalid second handshake occurs. The crash happens in the application's error handling path, where the gnutls_deinit function is called after detecting a handshake failure.

## Affected

- `gnutls < 3.6.15`
- `fedora = 32`
- `fedora = 33`
- `leap = 15.1`
- `leap = 15.2`
- `ubuntu_linux = 20.04`

## Remediation

Upgrade past the affected range:

- `gnutls 3.6.15`