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Fencer Intel
medium 5.3

CVE-2026-5950 json

Unbounded resend loop in BIND 9 resolver

published 5mo ago modified 3mo ago also EUVD-2026-31109

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 52%
public exploits
0
none known

Summary

An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad-server handling, enabling a remote unauthenticated attacker to cause severe resource exhaustion by sending queries that trigger specific retry conditions. This issue affects BIND 9 versions 9.18.36 through 9.18.48, 9.20.8 through 9.20.22, 9.21.7 through 9.21.21, 9.18.36-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

Patch / fix

  • isc bind 9.18.49, 9.20.23, 9.21.22
  • bind9 Debian 12 1:9.18.49-1~deb12u2
  • bind9 Debian 13 1:9.20.23-1~deb13u1
  • bind9 Debian 14 1:9.20.23-1

debian advisories DEBIAN-CVE-2026-5950

  • bind9 Ubuntu 22.04 LTS 1:9.18.39-0ubuntu0.22.04.4
  • bind9 Ubuntu 24.04 LTS 1:9.18.39-0ubuntu0.24.04.5
  • bind9 Ubuntu 25.10 1:9.20.11-1ubuntu2.4
  • bind9 Ubuntu 26.04 LTS 1:9.20.18-1ubuntu2.1

ubuntu advisories UBUNTU-CVE-2026-5950

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

  • bind hummingbird 1 9.18.49-1.hum1
  • bind-libs hummingbird 1 9.18.49-1.hum1
  • bind-utils hummingbird 1 9.18.49-1.hum1
  • bind-chroot hummingbird 1 9.18.49-1.hum1
  • bind-dnssec-utils hummingbird 1 9.18.49-1.hum1

red hat advisories RHSA-2026:20334

  • bind SLE Module for Server Applications 15 SP7, SLE Module for Basesystem 15 SP7 9.20.23-150700.3.25.1
  • bind SLES for SAP applications 16.0, SLES 16.0 9.20.23-160000.1.1
  • bind SLES for SAP 15 SP6, SLES 15 SP6-LTSS 9.18.49-150600.3.26.1

suse advisories SUSE-SU-2026:2673-1SUSE-SU-2026:2676-1SUSE-SU-2026:22198-1

  • bind openSUSE Leap 16.0 9.20.23-160000.1.1
  • bind openSUSE Tumbleweed 9.20.23-1.1

opensuse advisories openSUSE-SU-2026:21123-1openSUSE-SU-2026:10874-1

  • bind Alpine 3.21, Alpine 3.20 9.18.49-r0
  • bind Alpine 3.24, Alpine 3.23, Alpine 3.22 9.20.23-r0

alpine advisories ALPINE-CVE-2026-5950

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

  • bind Azure Linux 3.0 9.20.23-1

azure linux advisories AZL-87102

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

Is CVE-2026-5950 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

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-2026-5950 updated cvss 5.3

bind: Unbounded resend loop in BIND 9 resolver

  • Red Hat Enterprise Linux 6 bind, bind-sdb, bind-libs, bind-utils, bind-chroot Red Hat Enterprise Linux 7 bind, bind-sdb, bind-libs, bind-utils, bind-chroot, bind-pkcs11, +6 more Red Hat Enterprise Linux 8 bind, bind-sdb, bind9.16, bind-libs, bind-utils, bind-chroot, +14 more Red Hat Enterprise Linux 9 dhcp, dhcp-relay, dhcp-client, dhcp-common, dhcp-server 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 Enterprise Linux AppStream (v. 9) bind 9.16.50-11.el9_9, bind9.18 9.18.29-28.el9_9, bind-libs 9.16.50-11.el9_9, bind-utils 9.16.50-11.el9_9, bind-chroot 9.16.50-11.el9_9, bind-license 9.16.50-11.el9_9, +6 more
    fixed: vendor fix RHSA-2026:97586
  • Red Hat Enterprise Linux AppStream (v. 10) bind 9.18.33-29.el10_3, bind-libs 9.18.33-29.el10_3, bind-utils 9.18.33-29.el10_3, bind-chroot 9.18.33-29.el10_3, bind-license 9.18.33-29.el10_3, bind-dnssec-utils 9.18.33-29.el10_3
    fixed: vendor fix RHSA-2026:97242
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) bind-libs 9.16.50-11.el9_9, bind9.18-libs 9.18.29-28.el9_9
    fixed: vendor fix RHSA-2026:97586
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) bind-doc 9.18.33-29.el10_3, bind-devel 9.18.33-29.el10_3, bind-debuginfo 9.18.33-29.el10_3, bind-debugsource 9.18.33-29.el10_3, bind-libs-debuginfo 9.18.33-29.el10_3, bind-utils-debuginfo 9.18.33-29.el10_3, +1 more
    fixed: vendor fix RHSA-2026:97242
  • Red Hat Hardened Images bind 9.18.49-1.hum1, bind-libs 9.18.49-1.hum1, bind-utils 9.18.49-1.hum1, bind-chroot 9.18.49-1.hum1, bind-dnssec-utils 9.18.49-1.hum1
    fixed: vendor fix RHSA-2026:20334

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
5mo ago

Exploit prediction

0.66% chance of exploitation in the next 30 days, higher than 52% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected products

  • ISC BIND 9

Classification

Weakness
  • CWE-606 Unchecked Input for Loop Condition

References

Sources

Fencer Intel 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.