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Fencer Vulns
high 7.5

CVE-2020-24659 json

An issue was discovered in GnuTLS before 3.6.15.

published 2020-09-04 6 y ago modified 2026-10-14 26 d ago also EUVD-2020-17374 , JLSEC-2026-519

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.8%
EPSS 3.8% chance of exploitation in 30 days, percentile 90%
public exploits
0
none known

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 happens in the application's error handling path, where the gnutls_deinit function is called after detecting a handshake failure.

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 3.6.15-1

debian advisories DEBIAN-CVE-2020-24659

  • gnutls28 Ubuntu 20.04 LTS 3.6.13-2ubuntu1.3

ubuntu advisories UBUNTU-CVE-2020-24659

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 3.6.14-7.el8_3
  • gnutls-c++ RHEL 8 3.6.14-7.el8_3
  • gnutls-dane RHEL 8 3.6.14-7.el8_3
  • gnutls-utils RHEL 8 3.6.14-7.el8_3

red hat advisories RHSA-2020:5483

  • gnutls SLE Module for Certifications 15 SP3, SLE Module for Basesystem 15 SP2 3.6.7-14.4.1
  • gnutls SLES for SAP 15, SLES 15-LTSS, SLE Module for Basesystem 15 SP1 +2 more 3.6.7-6.34.1

suse advisories SUSE-SU-2020:2864-2SUSE-SU-2020:2988-1SUSE-SU-2020:2864-1

  • gnutls openSUSE Leap 15.2 3.6.7-lp152.9.3.2
  • gnutls openSUSE Leap 15.1 3.6.7-lp151.2.21.1

opensuse advisories openSUSE-SU-2020:1743-1openSUSE-SU-2020:1724-1

  • gnutls Alpine 3.24, Alpine 3.23, Alpine 3.22 +13 more 3.6.15-r0

alpine advisories ALPINE-CVE-2020-24659

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-6445

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

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-2020-24659 updated cvss 7.5

gnutls: Heap buffer overflow in handshake with no_renegotiation alert sent

  • Red Hat Enterprise Linux AppStream (v. 8) gnutls-c++ 3.6.14-7.el8_3, gnutls-dane 3.6.14-7.el8_3, gnutls-utils 3.6.14-7.el8_3 Red Hat Enterprise Linux BaseOS (v. 8) gnutls 3.6.14-7.el8_3
    fixed: vendor fix RHSA-2020:5483
  • Red Hat Enterprise Linux 5 gnutls Red Hat Enterprise Linux 6 gnutls, gnutls-guile, gnutls-utils Red Hat Enterprise Linux 7 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 7.5

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

Exploit prediction

3.83% chance of exploitation in the next 30 days, higher than 90% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • gitlab.com https://gitlab.com/gnutls/gnutls/-/issues/1071 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

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

Affected products

  • 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.