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Fencer Vulns
high 7.5

CVE-2026-42944 json

Heap overflow with multiple NSID, COOKIE, PADDING EDNS options

published 2026-05-20 5 mo ago modified 2026-08-26 2 mo ago also EUVD-2026-31085

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.8%
EPSS 0.8% chance of exploitation in 30 days, percentile 58%
public exploits
0
none known

Summary

NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a vulnerability that results in heap overflow when encoding multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options in the reply packet. The relevant options ('nsid', 'answer-cookie', 'pad-responses' (default)) need to be enabled for the vulnerability to be exploited. An adversary who can query Unbound can exploit the vulnerability by attaching multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options to the query. A flaw in the size calculation of the EDNS field truncates the correct value which allows the encoder to overflow the available space when writing. Those two combined lead to a heap overflow write of Unbound controlled data and eventually a crash. Unbound 1.25.1 contains a patch with a fix to de-duplicate the EDNS options and a fix to prevent truncation of the EDNS field size calculation.

Patch / fix

  • NLnet Labs Unbound 1.25.1
  • Red Hat Red Hat Enterprise Linux 10 0:1.24.2-7.el10_2.1
  • Red Hat Red Hat Enterprise Linux 8 0:1.16.2-5.11.el8_10
  • Red Hat Red Hat Enterprise Linux 9 0:1.24.2-3.el9_8.1
  • Red Hat Red Hat Hardened Images 1.25.1-0.1.hum1
  • unbound Debian 13 1.22.0-2+deb13u3
  • unbound Debian 14 1.25.1-1

debian advisories DEBIAN-CVE-2026-42944

  • unbound Ubuntu 24.04 LTS 1.19.2-1ubuntu3.8
  • unbound Ubuntu 25.10 1.22.0-2ubuntu2.3
  • unbound Ubuntu 26.04 LTS 1.24.2-1ubuntu2.1

ubuntu advisories UBUNTU-CVE-2026-42944

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

  • unbound RHEL 9 1.24.2-3.el9_8.1
  • unbound-libs RHEL 9 1.24.2-3.el9_8.1
  • unbound-dracut RHEL 9 1.24.2-3.el9_8.1
  • python3-unbound RHEL 9 1.24.2-3.el9_8.1
  • unbound RHEL 8 1.16.2-5.11.el8_10
  • unbound-libs RHEL 8 1.16.2-5.11.el8_10
  • python3-unbound RHEL 8 1.16.2-5.11.el8_10
  • unbound RHEL 10.2 1.24.2-7.el10_2.1

red hat advisories RHSA-2026:24369RHSA-2026:24365RHSA-2026:23231RHSA-2026:19752

  • unbound SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 1.24.1-160000.2.1
  • unbound SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +6 more 1.20.0-150100.10.25.1

suse advisories SUSE-SU-2026:22160-1SUSE-SU-2026:22213-1SUSE-SU-2026:2369-1

  • unbound openSUSE Leap 16.0 1.24.1-160000.2.1
  • unbound openSUSE Tumbleweed 1.25.1-1.1

opensuse advisories openSUSE-SU-2026:21083-1openSUSE-SU-2026:10903-1

  • unbound AlmaLinux 8 1.16.2-5.11.el8_10
  • unbound-libs AlmaLinux 8 1.16.2-5.11.el8_10
  • python3-unbound AlmaLinux 8 1.16.2-5.11.el8_10
  • unbound AlmaLinux 9 1.24.2-3.el9_8.1
  • unbound-libs AlmaLinux 9 1.24.2-3.el9_8.1
  • unbound-dracut AlmaLinux 9 1.24.2-3.el9_8.1
  • python3-unbound AlmaLinux 9 1.24.2-3.el9_8.1
  • unbound AlmaLinux 10 1.24.2-7.el10_2.1

almalinux advisories ALSA-2026:24365ALSA-2026:24369ALSA-2026:23231

  • unbound Rocky Linux 9 1.24.2-3.el9_8.1
  • unbound Rocky Linux 8 1.16.2-5.11.el8_10
  • unbound Rocky Linux 10 1.24.2-7.el10_2.1

rocky linux advisories RLSA-2026:24369RLSA-2026:24365RLSA-2026:23231

  • unbound Alpine 3.23, Alpine 3.22 1.25.2-r0
  • unbound Alpine 3.24 1.25.1-r0

alpine advisories ALPINE-CVE-2026-42944

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

  • unbound Azure Linux 3.0 1.25.1-1

azure linux advisories AZL-87042

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-2026-42944 updated cvss 7.5

unbound: Heap overflow and crash with multiple nsid, cookie, padding EDNS options

  • Red Hat Enterprise Linux 6 unbound, unbound-libs, unbound-python
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Enterprise Linux 7 unbound, unbound-libs, unbound-python
    affected: workaround, no fix available
  • Red Hat Enterprise Linux AppStream (v. 8) unbound 1.16.2-5.11.el8_10, unbound-libs 1.16.2-5.11.el8_10, python3-unbound 1.16.2-5.11.el8_10
    fixed: vendor fix RHSA-2026:24365
  • Red Hat Enterprise Linux AppStream (v. 9) unbound 1.24.2-3.el9_8.1, unbound-libs 1.24.2-3.el9_8.1, unbound-dracut 1.24.2-3.el9_8.1, python3-unbound 1.24.2-3.el9_8.1
    fixed: vendor fix RHSA-2026:24369
  • Red Hat Enterprise Linux AppStream (v. 10) unbound 1.24.2-7.el10_2.1, unbound-libs 1.24.2-7.el10_2.1, unbound-utils 1.24.2-7.el10_2.1, unbound-anchor 1.24.2-7.el10_2.1, unbound-dracut 1.24.2-7.el10_2.1, python3-unbound 1.24.2-7.el10_2.1
    fixed: vendor fix RHSA-2026:23231
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) unbound-devel 1.24.2-3.el9_8.1, unbound-debuginfo 1.24.2-3.el9_8.1, unbound-debugsource 1.24.2-3.el9_8.1, unbound-libs-debuginfo 1.24.2-3.el9_8.1, python3-unbound-debuginfo 1.24.2-3.el9_8.1
    fixed: vendor fix RHSA-2026:24369
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) unbound-devel 1.24.2-7.el10_2.1, unbound-debuginfo 1.24.2-7.el10_2.1, unbound-debugsource 1.24.2-7.el10_2.1, unbound-libs-debuginfo 1.24.2-7.el10_2.1, unbound-utils-debuginfo 1.24.2-7.el10_2.1, unbound-anchor-debuginfo 1.24.2-7.el10_2.1, +1 more
    fixed: vendor fix RHSA-2026:23231
  • Red Hat Hardened Images unbound 1.25.1-0.1.hum1, unbound-libs 1.25.1-0.1.hum1, unbound-munin 1.25.1-0.1.hum1, unbound-utils 1.25.1-0.1.hum1, unbound-anchor 1.25.1-0.1.hum1, unbound-dracut 1.25.1-0.1.hum1, +1 more
    fixed: vendor fix RHSA-2026:19752

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
5 mo ago

Exploit prediction

0.84% chance of exploitation in the next 30 days, higher than 58% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/U:Red
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 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Red
NVD 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

  • NLnet Labs Unbound
  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Hardened Images
  • Red Hat Red Hat Enterprise Linux 6
  • Red Hat Red Hat Enterprise Linux 7

Classification

Weakness
  • CWE-197 Numeric Truncation Error
  • CWE-787 Out-of-bounds Write
  • CWE-131 Incorrect Calculation of Buffer Size

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.