# CVE-2026-42944: Heap overflow with multiple NSID, COOKIE, PADDING EDNS options

CVE-2026-42944 is fixed in 15 products on 1 platform, first by libunbound8 1.24.2-1ubuntu2.1, released May 19, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-42944
- Priority: High
- CVSS: 8.1 (Moderate)
- EPSS: 0.0084
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 19, 2026
- Weakness: Numeric Truncation Error
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42944

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libunbound8 Ubuntu 24.04.5 LTS (noble) | 1.19.2-1ubuntu3.8 | [libunbound8 1.19.2-1ubuntu3.8](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libunbound8-1.19.2-1ubuntu3.8.md) | May 27, 2026 |
| Linux | libunbound8 Ubuntu 25.10 (questing) | 1.22.0-2ubuntu2.3 | [libunbound8 1.22.0-2ubuntu2.3](https://patchblox.com/security/data/fix/linux/ubuntu-questing-libunbound8-1.22.0-2ubuntu2.3.md) | May 27, 2026 |
| Linux | libunbound8 Ubuntu 26.04.1 LTS (resolute) | 1.24.2-1ubuntu2.1 | [libunbound8 1.24.2-1ubuntu2.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libunbound8-1.24.2-1ubuntu2.1.md) | May 19, 2026 |
| Linux | python3-unbound RHEL 8 | 0:1.16.2-5.11.el8_10 | [RHSA-2026:24365](https://patchblox.com/security/data/fix/linux/rhsa-2026-24365.md) | Jun 24, 2026 |
| Linux | python3-unbound RHEL 9 | 0:1.24.2-3.el9_8.1 | [RHSA-2026:24369](https://patchblox.com/security/data/fix/linux/rhsa-2026-24369.md) | Jun 24, 2026 |
| Linux | python3-unbound Ubuntu 24.04.5 LTS (noble) | 1.19.2-1ubuntu3.8 | [python3-unbound 1.19.2-1ubuntu3.8](https://patchblox.com/security/data/fix/linux/ubuntu-noble-python3-unbound-1.19.2-1ubuntu3.8.md) | May 27, 2026 |
| Linux | python3-unbound Ubuntu 25.10 (questing) | 1.22.0-2ubuntu2.3 | [python3-unbound 1.22.0-2ubuntu2.3](https://patchblox.com/security/data/fix/linux/ubuntu-questing-python3-unbound-1.22.0-2ubuntu2.3.md) | May 27, 2026 |
| Linux | python3-unbound Ubuntu 26.04.1 LTS (resolute) | 1.24.2-1ubuntu2.1 | [python3-unbound 1.24.2-1ubuntu2.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-python3-unbound-1.24.2-1ubuntu2.1.md) | May 19, 2026 |
| Linux | python3-unbound almalinux 10 | 1.24.2-7.el10_2.1 | [ALSA-2026:23231](https://patchblox.com/security/data/fix/linux/alsa-2026-23231.md) | Jun 4, 2026 |
| Linux | python3-unbound almalinux 8 | 1.16.2-5.11.el8_10 | [ALSA-2026:24365](https://patchblox.com/security/data/fix/linux/alsa-2026-24365.md) | Jun 8, 2026 |
| Linux | python3-unbound almalinux 9 | 1.24.2-3.el9_8.1 | [ALSA-2026:24369](https://patchblox.com/security/data/fix/linux/alsa-2026-24369.md) | Jun 8, 2026 |
| Linux | python3-unbound amzn 2023 | 1.17.1-1.amzn2023.0.12 | [ALAS2023-2026-1756](https://patchblox.com/security/data/fix/linux/alas2023-2026-1756.md) | May 25, 2026 |
| Linux | python3-unbound ol 10 | 0:1.24.2-7.el10_2.2 | [ELSA-2026-23231](https://patchblox.com/security/data/fix/linux/elsa-2026-23231.md) | Jul 21, 2026 |
| Linux | python3-unbound ol 8 | 0:1.16.2-5.11.el8_10 | [ELSA-2026-24365](https://patchblox.com/security/data/fix/linux/elsa-2026-24365.md) | Jun 8, 2026 |
| Linux | python3-unbound ol 9 | 0:1.24.2-3.el9_8.1 | [ELSA-2026-24369](https://patchblox.com/security/data/fix/linux/elsa-2026-24369.md) | Jun 23, 2026 |
| Linux | python3-unbound-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.12 | [ALAS2023-2026-1756](https://patchblox.com/security/data/fix/linux/alas2023-2026-1756.md) | May 25, 2026 |
| Linux | unbound Debian 13.5 (trixie) | 1.22.0-2+deb13u3 | [DEBIAN-CVE-2026-42944](https://patchblox.com/security/data/fix/linux/debian-cve-2026-42944.md) | May 27, 2026 |
| Linux | unbound Debian 14 | 1.25.1-1 | [DEBIAN-CVE-2026-42944](https://patchblox.com/security/data/fix/linux/debian-cve-2026-42944.md) | May 27, 2026 |
| Linux | unbound RHEL 10 | 1.24.2-7.el10_2.1 | [RHSA-2026:23231](https://patchblox.com/security/data/fix/linux/rhsa-2026-23231.md) | May 20, 2026 |
| Linux | unbound RHEL 8 | 0:1.16.2-5.11.el8_10 | [RHSA-2026:24365](https://patchblox.com/security/data/fix/linux/rhsa-2026-24365.md) | Jun 24, 2026 |
| Linux | unbound RHEL 9 | 0:1.24.2-3.el9_8.1 | [RHSA-2026:24369](https://patchblox.com/security/data/fix/linux/rhsa-2026-24369.md) | Jun 24, 2026 |
| Linux | unbound Ubuntu 24.04.5 LTS (noble) | 1.19.2-1ubuntu3.8 | [unbound 1.19.2-1ubuntu3.8](https://patchblox.com/security/data/fix/linux/ubuntu-noble-unbound-1.19.2-1ubuntu3.8.md) | May 27, 2026 |
| Linux | unbound Ubuntu 25.10 (questing) | 1.22.0-2ubuntu2.3 | [unbound 1.22.0-2ubuntu2.3](https://patchblox.com/security/data/fix/linux/ubuntu-questing-unbound-1.22.0-2ubuntu2.3.md) | May 27, 2026 |
| Linux | unbound Ubuntu 26.04.1 LTS (resolute) | 1.24.2-1ubuntu2.1 | [unbound 1.24.2-1ubuntu2.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-unbound-1.24.2-1ubuntu2.1.md) | May 19, 2026 |
| Linux | unbound almalinux 10 | 1.24.2-7.el10_2.1 | [ALSA-2026:23231](https://patchblox.com/security/data/fix/linux/alsa-2026-23231.md) | Jun 4, 2026 |
| Linux | unbound almalinux 8 | 1.16.2-5.11.el8_10 | [ALSA-2026:24365](https://patchblox.com/security/data/fix/linux/alsa-2026-24365.md) | Jun 8, 2026 |
| Linux | unbound almalinux 9 | 1.24.2-3.el9_8.1 | [ALSA-2026:24369](https://patchblox.com/security/data/fix/linux/alsa-2026-24369.md) | Jun 8, 2026 |
| Linux | unbound amzn 2023 | 1.17.1-1.amzn2023.0.12 | [ALAS2023-2026-1756](https://patchblox.com/security/data/fix/linux/alas2023-2026-1756.md) | May 25, 2026 |
| Linux | unbound ol 10 | 0:1.24.2-7.el10_2.2 | [ELSA-2026-23231](https://patchblox.com/security/data/fix/linux/elsa-2026-23231.md) | Jul 21, 2026 |
| Linux | unbound ol 8 | 0:1.16.2-5.11.el8_10 | [ELSA-2026-24365](https://patchblox.com/security/data/fix/linux/elsa-2026-24365.md) | Jun 8, 2026 |
| Linux | unbound ol 9 | 0:1.24.2-3.el9_8.1 | [ELSA-2026-24369](https://patchblox.com/security/data/fix/linux/elsa-2026-24369.md) | Jun 23, 2026 |
| Linux | unbound opensuse-leap 16.0 | 1.24.1-160000.2.1 | [OPENSUSE-SU-2026:21083-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21083-1.md) | Jun 18, 2026 |
| Linux | unbound rocky 10 | 0:1.24.2-7.el10_2.1 | [RLSA-2026:23231](https://patchblox.com/security/data/fix/linux/rlsa-2026-23231.md) | Jun 6, 2026 |
| Linux | unbound rocky 8 | 0:1.16.2-5.11.el8_10 | [RLSA-2026:24365](https://patchblox.com/security/data/fix/linux/rlsa-2026-24365.md) | Jun 11, 2026 |
| Linux | unbound rocky 9 | 0:1.24.2-3.el9_8.1 | [RLSA-2026:24369](https://patchblox.com/security/data/fix/linux/rlsa-2026-24369.md) | Jun 11, 2026 |
| Linux | unbound sles 16.0 | 1.24.1-160000.2.1 | [SUSE-SU-2026:22160-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-22160-1.md) | Jun 18, 2026 |
| Linux | unbound-anchor Ubuntu 24.04.5 LTS (noble) | 1.19.2-1ubuntu3.8 | [unbound-anchor 1.19.2-1ubuntu3.8](https://patchblox.com/security/data/fix/linux/ubuntu-noble-unbound-anchor-1.19.2-1ubuntu3.8.md) | May 27, 2026 |
| Linux | unbound-anchor Ubuntu 25.10 (questing) | 1.22.0-2ubuntu2.3 | [unbound-anchor 1.22.0-2ubuntu2.3](https://patchblox.com/security/data/fix/linux/ubuntu-questing-unbound-anchor-1.22.0-2ubuntu2.3.md) | May 27, 2026 |
| Linux | unbound-anchor Ubuntu 26.04.1 LTS (resolute) | 1.24.2-1ubuntu2.1 | [unbound-anchor 1.24.2-1ubuntu2.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-unbound-anchor-1.24.2-1ubuntu2.1.md) | May 19, 2026 |
| Linux | unbound-anchor almalinux 10 | 1.24.2-7.el10_2.1 | [ALSA-2026:23231](https://patchblox.com/security/data/fix/linux/alsa-2026-23231.md) | Jun 4, 2026 |
| Linux | unbound-anchor amzn 2023 | 1.17.1-1.amzn2023.0.12 | [ALAS2023-2026-1756](https://patchblox.com/security/data/fix/linux/alas2023-2026-1756.md) | May 25, 2026 |
| Linux | unbound-anchor ol 10 | 0:1.24.2-7.el10_2.2 | [ELSA-2026-23231](https://patchblox.com/security/data/fix/linux/elsa-2026-23231.md) | Jul 21, 2026 |
| Linux | unbound-anchor-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.12 | [ALAS2023-2026-1756](https://patchblox.com/security/data/fix/linux/alas2023-2026-1756.md) | May 25, 2026 |
| Linux | unbound-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.12 | [ALAS2023-2026-1756](https://patchblox.com/security/data/fix/linux/alas2023-2026-1756.md) | May 25, 2026 |
| Linux | unbound-debugsource amzn 2023 | 1.17.1-1.amzn2023.0.12 | [ALAS2023-2026-1756](https://patchblox.com/security/data/fix/linux/alas2023-2026-1756.md) | May 25, 2026 |
| Linux | unbound-devel RHEL 8 | 0:1.16.2-5.11.el8_10 | [RHSA-2026:24365](https://patchblox.com/security/data/fix/linux/rhsa-2026-24365.md) | Jun 24, 2026 |
| Linux | unbound-devel RHEL 9 | 0:1.24.2-3.el9_8.1 | [RHSA-2026:24369](https://patchblox.com/security/data/fix/linux/rhsa-2026-24369.md) | Jun 24, 2026 |
| Linux | unbound-devel almalinux 10 | 1.24.2-7.el10_2.1 | [ALSA-2026:23231](https://patchblox.com/security/data/fix/linux/alsa-2026-23231.md) | Jun 4, 2026 |
| Linux | unbound-devel almalinux 8 | 1.16.2-5.11.el8_10 | [ALSA-2026:24365](https://patchblox.com/security/data/fix/linux/alsa-2026-24365.md) | Jun 8, 2026 |
| Linux | unbound-devel almalinux 9 | 1.24.2-3.el9_8.1 | [ALSA-2026:24369](https://patchblox.com/security/data/fix/linux/alsa-2026-24369.md) | Jun 8, 2026 |
| Linux | unbound-devel amzn 2023 | 1.17.1-1.amzn2023.0.12 | [ALAS2023-2026-1756](https://patchblox.com/security/data/fix/linux/alas2023-2026-1756.md) | May 25, 2026 |
| Linux | unbound-devel ol 10 | 0:1.24.2-7.el10_2.2 | [ELSA-2026-23231](https://patchblox.com/security/data/fix/linux/elsa-2026-23231.md) | Jul 21, 2026 |
| Linux | unbound-devel ol 8 | 0:1.16.2-5.11.el8_10 | [ELSA-2026-24365](https://patchblox.com/security/data/fix/linux/elsa-2026-24365.md) | Jun 8, 2026 |
| Linux | unbound-devel ol 9 | 0:1.24.2-3.el9_8.1 | [ELSA-2026-24369](https://patchblox.com/security/data/fix/linux/elsa-2026-24369.md) | Jun 23, 2026 |
| Linux | unbound-dracut RHEL 9 | 0:1.24.2-3.el9_8.1 | [RHSA-2026:24369](https://patchblox.com/security/data/fix/linux/rhsa-2026-24369.md) | Jun 24, 2026 |
| Linux | unbound-dracut almalinux 10 | 1.24.2-7.el10_2.1 | [ALSA-2026:23231](https://patchblox.com/security/data/fix/linux/alsa-2026-23231.md) | Jun 4, 2026 |
| Linux | unbound-dracut almalinux 9 | 1.24.2-3.el9_8.1 | [ALSA-2026:24369](https://patchblox.com/security/data/fix/linux/alsa-2026-24369.md) | Jun 8, 2026 |
| Linux | unbound-dracut ol 10 | 0:1.24.2-7.el10_2.2 | [ELSA-2026-23231](https://patchblox.com/security/data/fix/linux/elsa-2026-23231.md) | Jul 21, 2026 |
| Linux | unbound-dracut ol 9 | 0:1.24.2-3.el9_8.1 | [ELSA-2026-24369](https://patchblox.com/security/data/fix/linux/elsa-2026-24369.md) | Jun 23, 2026 |
| Linux | unbound-host Ubuntu 24.04.5 LTS (noble) | 1.19.2-1ubuntu3.8 | [unbound-host 1.19.2-1ubuntu3.8](https://patchblox.com/security/data/fix/linux/ubuntu-noble-unbound-host-1.19.2-1ubuntu3.8.md) | May 27, 2026 |
| Linux | unbound-host Ubuntu 25.10 (questing) | 1.22.0-2ubuntu2.3 | [unbound-host 1.22.0-2ubuntu2.3](https://patchblox.com/security/data/fix/linux/ubuntu-questing-unbound-host-1.22.0-2ubuntu2.3.md) | May 27, 2026 |
| Linux | unbound-host Ubuntu 26.04.1 LTS (resolute) | 1.24.2-1ubuntu2.1 | [unbound-host 1.24.2-1ubuntu2.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-unbound-host-1.24.2-1ubuntu2.1.md) | May 19, 2026 |
| Linux | unbound-libs RHEL 8 | 0:1.16.2-5.11.el8_10 | [RHSA-2026:24365](https://patchblox.com/security/data/fix/linux/rhsa-2026-24365.md) | Jun 24, 2026 |
| Linux | unbound-libs RHEL 9 | 0:1.24.2-3.el9_8.1 | [RHSA-2026:24369](https://patchblox.com/security/data/fix/linux/rhsa-2026-24369.md) | Jun 24, 2026 |
| Linux | unbound-libs almalinux 10 | 1.24.2-7.el10_2.1 | [ALSA-2026:23231](https://patchblox.com/security/data/fix/linux/alsa-2026-23231.md) | Jun 4, 2026 |
| Linux | unbound-libs almalinux 8 | 1.16.2-5.11.el8_10 | [ALSA-2026:24365](https://patchblox.com/security/data/fix/linux/alsa-2026-24365.md) | Jun 8, 2026 |
| Linux | unbound-libs almalinux 9 | 1.24.2-3.el9_8.1 | [ALSA-2026:24369](https://patchblox.com/security/data/fix/linux/alsa-2026-24369.md) | Jun 8, 2026 |
| Linux | unbound-libs amzn 2023 | 1.17.1-1.amzn2023.0.12 | [ALAS2023-2026-1756](https://patchblox.com/security/data/fix/linux/alas2023-2026-1756.md) | May 25, 2026 |
| Linux | unbound-libs ol 10 | 0:1.24.2-7.el10_2.2 | [ELSA-2026-23231](https://patchblox.com/security/data/fix/linux/elsa-2026-23231.md) | Jul 21, 2026 |
| Linux | unbound-libs ol 8 | 0:1.16.2-5.11.el8_10 | [ELSA-2026-24365](https://patchblox.com/security/data/fix/linux/elsa-2026-24365.md) | Jun 8, 2026 |
| Linux | unbound-libs ol 9 | 0:1.24.2-3.el9_8.1 | [ELSA-2026-24369](https://patchblox.com/security/data/fix/linux/elsa-2026-24369.md) | Jun 23, 2026 |
| Linux | unbound-libs-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.12 | [ALAS2023-2026-1756](https://patchblox.com/security/data/fix/linux/alas2023-2026-1756.md) | May 25, 2026 |
| Linux | unbound-utils almalinux 10 | 1.24.2-7.el10_2.1 | [ALSA-2026:23231](https://patchblox.com/security/data/fix/linux/alsa-2026-23231.md) | Jun 4, 2026 |
| Linux | unbound-utils amzn 2023 | 1.17.1-1.amzn2023.0.12 | [ALAS2023-2026-1756](https://patchblox.com/security/data/fix/linux/alas2023-2026-1756.md) | May 25, 2026 |
| Linux | unbound-utils ol 10 | 0:1.24.2-7.el10_2.2 | [ELSA-2026-23231](https://patchblox.com/security/data/fix/linux/elsa-2026-23231.md) | Jul 21, 2026 |
| Linux | unbound-utils-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.12 | [ALAS2023-2026-1756](https://patchblox.com/security/data/fix/linux/alas2023-2026-1756.md) | May 25, 2026 |

---

Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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