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Fencer Vulns
critical 9.8

CVE-2021-20232 json

A flaw was found in gnutls.

published 2021-03-12 5 y ago modified 2026-10-14 26 d ago also EUVD-2021-7671 , JLSEC-2026-521

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
3.4%
EPSS 3.4% chance of exploitation in 30 days, percentile 88%
public exploits
0
none known

Summary

A flaw was found in gnutls. A use after free issue in client_send_params in lib/ext/pre_shared_key.c may lead to memory corruption and other potential consequences.

Patch / fix

  • julia GnuTLS_jll 3.7.1+0
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • gnutls28 Debian 14, Debian 13, Debian 12 3.7.1-1

debian advisories DEBIAN-CVE-2021-20232

  • gnutls28 Ubuntu 20.04 LTS 3.6.13-2ubuntu1.6

ubuntu advisories UBUNTU-CVE-2021-20232

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • gnutls RHEL 8 3.6.16-4.el8
  • nettle RHEL 8 3.4.1-7.el8
  • gnutls-c++ RHEL 8 3.6.16-4.el8
  • gnutls-dane RHEL 8 3.6.16-4.el8
  • gnutls-utils RHEL 8 3.6.16-4.el8

red hat advisories RHSA-2021:4451

  • gnutls SLE Module for Basesystem 15 SP2, SLE Micro 5.0 3.6.7-14.10.2
  • gnutls SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +10 more 3.6.7-6.40.2

suse advisories SUSE-SU-2021:0935-1SUSE-SU-2021:0934-1

  • gnutls openSUSE Tumbleweed 3.7.2-1.2
  • gnutls openSUSE Leap 15.2 3.6.7-lp152.9.9.1

opensuse advisories openSUSE-SU-2024:10801-1openSUSE-SU-2021:0470-1

  • gnutls AlmaLinux 8 3.6.16-4.el8
  • nettle AlmaLinux 8 3.4.1-7.el8
  • gnutls-c++ AlmaLinux 8 3.6.16-4.el8
  • gnutls-dane AlmaLinux 8 3.6.16-4.el8
  • gnutls-utils AlmaLinux 8 3.6.16-4.el8

almalinux advisories ALSA-2021:4451

  • gnutls Rocky Linux 8 3.6.16-4.el8
  • nettle Rocky Linux 8 3.4.1-7.el8

rocky linux advisories RLSA-2021:4451

  • gnutls Alpine 3.12, Alpine 3.11, Alpine 3.10 3.6.15-r1
  • gnutls Alpine 3.24, Alpine 3.23, Alpine 3.22 +9 more 3.7.1-r0

alpine advisories ALPINE-CVE-2021-20232

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • gnutls CBL-Mariner 2.0 3.6.14-5

azure linux advisories AZL-6447

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

  • gnutls Arch Linux 3.7.1-1

arch linux advisories AVG-1674

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-20232 updated cvss 3.7

gnutls: Use after free in client_send_params in lib/ext/pre_shared_key.c

  • Red Hat Enterprise Linux AppStream (v. 8) gnutls-c++ 3.6.16-4.el8, gnutls-dane 3.6.16-4.el8, gnutls-utils 3.6.16-4.el8 Red Hat Enterprise Linux BaseOS (v. 8) nettle 3.4.1-7.el8, gnutls 3.6.16-4.el8
    fixed: vendor fix RHSA-2021:4451
  • Red Hat Enterprise Linux 6 gnutls, gnutls-guile, gnutls-utils Red Hat Enterprise Linux 7 gnutls, gnutls-c++, gnutls-dane, gnutls-utils Red Hat Enterprise Linux 9 gnutls, gnutls-c++, gnutls-dane, gnutls-utils
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-23-348-10 updated cvss 9.8

Siemens SIMATIC S7-1500

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.0, < 3.1.5
    affected: fixed in V3.1.5, mitigation support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
11 mo ago

Exploit prediction

3.38% chance of exploitation in the next 30 days, higher than 88% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P
OSV 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
julia GnuTLS_jll
<3.7.1+0
3.7.1+0

Affected products

  • n/a gnutls
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.