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Fencer Vulns
high 8.6

CVE-2021-3517 in the critical feed json

Nokogiri contains libxml Out-of-bounds Write vulnerability

published 2021-05-19 5 y ago modified 2026-10-14 26 d ago also EUVD-2022-4443 , GHSA-jw9f-hh49-cvp9 , JLSEC-2025-72

cvss
8.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
17.0%
EPSS 17.0% chance of exploitation in 30 days, percentile 97%
public exploits
0
none known

Summary

There is a flaw in the xml entity encoding functionality of libxml2 in versions before 2.9.11. An attacker who is able to supply a crafted file to be processed by an application linked with the affected functionality of libxml2 could trigger an out-of-bounds read. The most likely impact of this flaw is to application availability, with some potential impact to confidentiality and integrity if an attacker is able to use memory information to further exploit the application.

Patch / fix

  • rubygems nokogiri 1.11.4
  • julia XML2_jll 2.9.12+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
  • libxml2 Debian 14, Debian 13, Debian 12 2.9.10+dfsg-6.6

debian advisories DEBIAN-CVE-2021-3517

  • libxml2 Ubuntu 18.04 LTS 2.9.4+dfsg1-6.1ubuntu1.4
  • libxml2 Ubuntu 20.04 LTS 2.9.10+dfsg-5ubuntu0.20.04.1
  • libxml2 Ubuntu Pro 14.04 LTS 2.9.1+dfsg1-3ubuntu4.13+esm2
  • libxml2 Ubuntu Pro 16.04 LTS 2.9.3+dfsg1-1ubuntu0.7+esm1

ubuntu advisories UBUNTU-CVE-2021-3517

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

  • jbcs-httpd24-curl jboss core services 1 7.78.0-3.jbcs.el7
  • jbcs-httpd24-curl jboss core services 1 7.78.0-3.el8jbcs
  • jbcs-httpd24-httpd jboss core services 1 2.4.37-80.jbcs.el7
  • jbcs-httpd24-httpd jboss core services 1 2.4.37-80.el8jbcs
  • jbcs-httpd24-mod_jk jboss core services 1 1.2.48-29.redhat_1.jbcs.el7
  • jbcs-httpd24-mod_jk jboss core services 1 1.2.48-29.redhat_1.el8jbcs
  • jbcs-httpd24-mod_md jboss core services 1 1:2.0.8-41.jbcs.el7
  • jbcs-httpd24-mod_md jboss core services 1 1:2.0.8-41.el8jbcs

red hat advisories RHSA-2022:1389RHSA-2021:2569

  • libxml2 SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +11 more 2.9.4-46.43.1
  • python-libxml2 SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +10 more 2.9.4-46.43.1
  • libxml2 SLE Module for Basesystem 15 SP3, SLE Module for Basesystem 15 SP2, SLE Micro 5.0 2.9.7-3.34.1
  • python-libxml2-python SLE Module for Python 2 15 SP3, SLE Module for Python 2 15 SP2, SLE Module for Basesystem 15 SP3 +1 more 2.9.7-3.34.1
  • libxml2 SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 2.7.6-0.77.36.1
  • libxml2-python SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 2.7.6-0.77.36.1
  • libxml2 SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 2.9.4-46.40.1
  • python-libxml2 SLES for SAP 12 SP5, SLES 12 SP5 2.9.4-46.40.1

suse advisories SUSE-SU-2021:1658-1SUSE-SU-2021:1654-1SUSE-SU-2021:14729-1SUSE-SU-2021:1524-1SUSE-SU-2021:1523-1

  • rubygem-nokogiri openSUSE Tumbleweed 1.18.9-1.4
  • rubygem-nokogiri openSUSE Tumbleweed 1.18.2-1.1
  • rubygem-nokogiri openSUSE Tumbleweed 1.15.5-1.5
  • libxml2 openSUSE Tumbleweed 2.9.12-1.2
  • rubygem-nokogiri openSUSE Tumbleweed 1.13.3-1.1
  • ruby3.2-rubygem-nokogiri openSUSE Tumbleweed 1.13.9-1.7
  • libxml2 openSUSE Leap 15.2 2.9.7-lp152.10.12.1
  • python-libxml2-python openSUSE Leap 15.2 2.9.7-lp152.10.12.1

opensuse advisories openSUSE-SU-2026:10356-1openSUSE-SU-2025:14697-1openSUSE-SU-2024:14174-1openSUSE-SU-2024:11016-1openSUSE-SU-2024:11912-1openSUSE-SU-2024:13165-1

  • libxml2 Rocky Linux 8 2.9.7-9.el8_4.2

rocky linux advisories RLSA-2021:2569

  • libxml2 Alpine 3.10 2.9.9-r5
  • libxml2 Alpine 3.11 2.9.10-r5
  • libxml2 Alpine 3.12 2.9.10-r6
  • libxml2 Alpine 3.13 2.9.10-r7
  • libxml2 Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 2.9.11-r0
  • qt5-qtwebengine Alpine 3.23, Alpine 3.22, Alpine 3.21 +7 more 5.15.3_git20211112-r0

alpine advisories ALPINE-CVE-2021-3517

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

  • libxml2 Arch Linux 2.9.11-1

arch linux advisories AVG-1883

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-2021-3517 updated cvss 8.6

libxml2: Heap-based buffer overflow in xmlEncodeEntitiesInternal() in entities.c

  • Red Hat Enterprise Linux 6 libxml2, compat-expat1, libxml2-python Red Hat Enterprise Linux 7 libxml2, libxml2-python
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) libxml2-devel 2.9.7-9.el8_4.2, libxml2-debuginfo 2.9.7-9.el8_4.2, libxml2-debugsource 2.9.7-9.el8_4.2, python3-libxml2-debuginfo 2.9.7-9.el8_4.2 Red Hat Enterprise Linux BaseOS (v. 8) libxml2 2.9.7-9.el8_4.2, python3-libxml2 2.9.7-9.el8_4.2
    fixed: vendor fix RHSA-2021:2569
  • Red Hat JBoss Core Services
    fixed: vendor fix RHSA-2022:1390
  • Red Hat JBoss Core Services on RHEL 7 Server jbcs-httpd24-curl 7.78.0-3.jbcs.el7, jbcs-httpd24-httpd 2.4.37-80.jbcs.el7, jbcs-httpd24-mod_md 2.0.8-41.jbcs.el7, jbcs-httpd24-libcurl 7.78.0-3.jbcs.el7, jbcs-httpd24-apr-util 1.6.1-91.jbcs.el7, jbcs-httpd24-mod_ssl 2.4.37-80.jbcs.el7, +25 more Red Hat JBoss Core Services on RHEL 8 jbcs-httpd24-curl 7.78.0-3.el8jbcs, jbcs-httpd24-httpd 2.4.37-80.el8jbcs, jbcs-httpd24-mod_md 2.0.8-41.el8jbcs, jbcs-httpd24-libcurl 7.78.0-3.el8jbcs, jbcs-httpd24-apr-util 1.6.1-91.el8jbcs, jbcs-httpd24-mod_ssl 2.4.37-80.el8jbcs, +25 more
    fixed: vendor fix RHSA-2022:1389
  • Red Hat Migration Toolkit 1.4 rhmtc/openshift-migration-ui-rhel8 v1.4.6-4, rhmtc/openshift-velero-plugin-rhel8 v1.4.6-4, rhmtc/openshift-migration-velero-rhel8 v1.4.6-5, rhmtc/openshift-migration-registry-rhel8 v1.4.6-4, rhmtc/openshift-migration-operator-bundle v1.4.6-5, rhmtc/openshift-migration-controller-rhel8 v1.4.6-4, +7 more
    fixed: vendor fix RHBA-2021:2854
  • Red Hat Enterprise Linux 9 libxml2, python3-libxml2
    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 8.6

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 ICSA-21-336-06 updated cvss 8.6

Hitachi Energy APM Edge

  • Hitachi Energy APM Edge 3.0, 2.0, 1.0
    affected: vendor fix, mitigation “Physically protect process control systems from direct access by unauthorized personnel.” search.abb.com

From CISA ICS and IT advisories (CSAF, https://github.com/cisagov/CSAF), a U.S. Government work; changed: reduced to products, statuses and remediations. CISA notification · csaf

cisa ICSA-21-336-08 updated cvss 8.6

Hitachi Energy RTU500 series

  • Hitachi Energy RTU500 series CMU Firmware 12.2.*, 13.1.*, 13.0.*, 12.0.*
    affected: vendor fix, mitigation “Physically protect process control systems from direct access by unauthorized personnel.” search.abb.com

From CISA ICS and IT advisories (CSAF, https://github.com/cisagov/CSAF), a U.S. Government work; changed: reduced to products, statuses and remediations. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
11 mo ago

Exploit prediction

16.99% chance of exploitation in the next 30 days, higher than 97% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
GitHub 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
NVD 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
CNA 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P
OSV 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

Affected packages

ecosystem package affected fixed in
rubygems nokogiri
<1.11.4
1.11.4
julia XML2_jll
<2.9.12+0
2.9.12+0

Affected products

  • n/a libxml2
  • 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.