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Fencer Vulns
high 7.5

CVE-2026-4437 json

gethostbyaddr and gethostbyaddr_r may incorrectly handle DNS response

published 2026-03-20 7 mo ago modified 2026-10-15 25 d ago also EUVD-2026-13796

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

Summary

Calling gethostbyaddr or gethostbyaddr_r with a configured nsswitch.conf that specifies the library's DNS backend in the GNU C Library version 2.34 to version 2.43 could, with a crafted response from the configured DNS server, result in a violation of the DNS specification that causes the application to treat a non-answer section of the DNS response as a valid answer.

Patch / fix

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.6
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.6
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.6
  • glibc Debian 12 2.36-9+deb12u14
  • glibc Debian 13 2.41-12+deb13u3
  • glibc Debian 14 2.42-14

debian advisories DEBIAN-CVE-2026-4437

  • glibc Ubuntu 24.04 LTS 2.39-0ubuntu8.8

ubuntu advisories UBUNTU-CVE-2026-4437

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

  • glibc RHEL 9 2.34-270.el9_8
  • nscd RHEL 9 2.34-270.el9_8
  • libnsl RHEL 9 2.34-270.el9_8
  • nss_db RHEL 9 2.34-270.el9_8
  • nss_hesiod RHEL 9 2.34-270.el9_8
  • glibc-utils RHEL 9 2.34-270.el9_8
  • glibc-common RHEL 9 2.34-270.el9_8
  • glibc-benchtests RHEL 9 2.34-270.el9_8

red hat advisories RHSA-2026:20597RHSA-2026:19061RHSA-2026:7316

  • glibc SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Development Tools 15 SP7 +2 more 2.38-150600.14.46.1
  • glibc SLES 16.0, Linux Micro Extras 6.2, Linux Micro 6.2 +1 more 2.40-160000.4.1
  • glibc Linux Micro 6.1 2.38-slfo.1.1_7.1
  • glibc Linux Micro 6.0 2.38-12.1

suse advisories SUSE-SU-2026:1369-1SUSE-SU-2026:21019-1SUSE-SU-2026:21164-1SUSE-SU-2026:20999-1SUSE-SU-2026:21039-1SUSE-SU-2026:21069-1

  • glibc openSUSE Tumbleweed 2.43-1.1
  • glibc openSUSE Leap 16.0 2.40-160000.4.1
  • glibc-cross-s390x-src openSUSE Leap 16.0 2.40-160000.4.1
  • glibc-cross-aarch64-src openSUSE Leap 16.0 2.40-160000.4.1
  • glibc-cross-ppc64le-src openSUSE Leap 16.0 2.40-160000.4.1
  • glibc-cross-riscv64-src openSUSE Leap 16.0 2.40-160000.4.1

opensuse advisories openSUSE-SU-2026:10662-1openSUSE-SU-2026:20501-1

  • glibc AlmaLinux 9 2.34-270.el9_8
  • nscd AlmaLinux 9 2.34-270.el9_8
  • libnsl AlmaLinux 9 2.34-270.el9_8
  • nss_db AlmaLinux 9 2.34-270.el9_8
  • nss_hesiod AlmaLinux 9 2.34-270.el9_8
  • glibc-utils AlmaLinux 9 2.34-270.el9_8
  • glibc-common AlmaLinux 9 2.34-270.el9_8
  • glibc-benchtests AlmaLinux 9 2.34-270.el9_8

almalinux advisories ALSA-2026:20597ALSA-2026:19061

  • glibc Rocky Linux 9 2.34-270.el9_8
  • glibc Rocky Linux 10 2.39-121.el10_2

rocky linux advisories RLSA-2026:20597RLSA-2026:19061

  • glibc Azure Linux 3.0 2.38-19

azure linux advisories AZL-80279

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-2026-4437 updated cvss 6.5

glibc: glibc: Incorrect DNS response parsing via crafted DNS server response

  • Red Hat Enterprise Linux 6 nscd, glibc, glibc-utils, compat-glibc, glibc-common Red Hat Enterprise Linux 7 nscd, glibc, glibc-utils, compat-glibc, glibc-common Red Hat Enterprise Linux 8 nscd, glibc, libnsl, nss_db, nss_hesiod, glibc-utils, +7 more Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat OpenShift Container Platform 4 openshift4/ose-hypershift-rhel9
    under investigation
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.17 cert-manager/cert-manager-operator-rhel9 1791788287, cert-manager/jetstack-cert-manager-rhel9 1791371069, cert-manager/cert-manager-operator-bundle 1791970484, cert-manager/jetstack-cert-manager-acmesolver-rhel9 1791371080
    fixed: vendor fix RHSA-2026:82888
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.18 cert-manager/cert-manager-operator-rhel9 1789029076, cert-manager/jetstack-cert-manager-rhel9 1791459711, cert-manager/cert-manager-istio-csr-rhel9 1791459759, cert-manager/cert-manager-operator-bundle 1791966259, cert-manager/jetstack-cert-manager-acmesolver-rhel9 1791459707
    fixed: vendor fix RHSA-2026:82354
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.20 cert-manager/cert-manager-trust-manager-rhel9 1790598593
    fixed: vendor fix RHSA-2026:72502
  • Red Hat Cost Management 4 costmanagement/costmanagement-metrics-rhel9-operator 1780946239
    fixed: vendor fix RHSA-2026:27998
  • Red Hat Discovery 2 discovery/discovery-ui-rhel9 1782166952, discovery/discovery-server-rhel9 1782159791
    fixed: vendor fix RHSA-2026:29197
  • Red Hat Enterprise Linux AppStream (v. 9) glibc-utils 2.34-270.el9_8, glibc-locale-source 2.34-270.el9_8
    fixed: vendor fix RHSA-2026:20597
show 9 more
  • Red Hat Enterprise Linux AppStream (v. 10) glibc-utils 2.39-121.el10_2, glibc-locale-source 2.39-121.el10_2
    fixed: vendor fix RHSA-2026:19061
  • Red Hat Enterprise Linux BaseOS (v. 9) nscd 2.34-270.el9_8, glibc 2.34-270.el9_8, libnsl 2.34-270.el9_8, glibc-common 2.34-270.el9_8, glibc-gconv-extra 2.34-270.el9_8, glibc-all-langpacks 2.34-270.el9_8, +1 more
    fixed: vendor fix RHSA-2026:20597
  • Red Hat Enterprise Linux BaseOS (v. 10) glibc 2.39-121.el10_2, libnsl 2.39-121.el10_2, glibc-common 2.39-121.el10_2, glibc-gconv-extra 2.39-121.el10_2, glibc-all-langpacks 2.39-121.el10_2, glibc-minimal-langpack 2.39-121.el10_2
    fixed: vendor fix RHSA-2026:19061
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) nss_db 2.34-270.el9_8, nss_hesiod 2.34-270.el9_8, glibc-benchtests 2.34-270.el9_8
    fixed: vendor fix RHSA-2026:20597
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) nss_db 2.39-121.el10_2, nss_hesiod 2.39-121.el10_2, glibc-benchtests 2.39-121.el10_2
    fixed: vendor fix RHSA-2026:19061
  • Red Hat Hardened Images glibc 2.42-11.1.hum1, glibc32 2.42-11.1.hum1, glibc-utils 2.42-11.1.hum1, glibc-common 2.42-11.1.hum1, glibc-benchtests 2.42-11.1.hum1, glibc-gconv-extra 2.42-11.1.hum1, +5 more
    fixed: vendor fix RHSA-2026:7316
  • Red Hat Insights proxy 1.5 insights-proxy/insights-proxy-container-rhel9 1780420428
    fixed: vendor fix RHSA-2026:22634
  • Red Hat Update Infrastructure 5 rhui5/cds-rhel9 1781525684, rhui5/rhua-rhel9 1781525739, rhui5/haproxy-rhel9 1781525671, rhui5/rhua-tp-rhel9 1787241260, rhui5/installer-rhel9 1781525693, rhui5/installer-tp-rhel9 1787135742, +1 more
    fixed: vendor fix RHSA-2026:58981
  • Red Hat Cost Management 4 costmanagement/costmanagement-metrics-operator-bundle 1780989656 Red Hat Hardened Images libnsl 2.42-11.1.hum1, nss_db 2.42-11.1.hum1, nss_hesiod 2.42-11.1.hum1, compat-libpthread-nonshared 2.42-11.1.hum1 Red Hat Update Infrastructure 5 rhui5/cds-tp-rhel9 1787241206, rhui5/cds-kubernetes-rhel9 1781525677
    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 SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • sourceware.org https://sourceware.org/bugzilla/show_bug.cgi?id=34014 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

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

Affected products

  • The GNU C Library glibc
  • 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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.