# CVE-2026-33278: Possible arbitrary code execution during DNSSEC validation

CVE-2026-33278 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: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-33278
- Priority: Urgent
- CVSS: 9.8 (Critical)
- EPSS: 0.0142
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 19, 2026
- Weakness: Use After Free
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-33278

## Description

NLnet Labs Unbound 1.19.1 up to and including version 1.25.0 has a vulnerability in the DNSSEC validator that enables denial of service and possible remote code execution as a result of deep copying a data structure and erroneously overwriting a destination pointer. An adversary can exploit the vulnerability by controlling a malicious signed zone and querying a vulnerable Unbound. When DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1), Unbound deep-copies response messages to preserve them across memory region teardown. A struct-assignment bug overwrites the destination's pointer with the source's pointer. After the sub-query region is freed, the resumed validator dereferences this dangling pointer, triggering a crash or potentially enabling arbitrary code execution. Unbound 1.25.1 contains a patch with a fix to preserve the correct pointer when deep copying the data structure.

## 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 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 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 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-2026-33278](https://patchblox.com/security/data/fix/linux/debian-cve-2026-33278.md) | May 27, 2026 |
| Linux | unbound Debian 14 | 1.25.1-1 | [DEBIAN-CVE-2026-33278](https://patchblox.com/security/data/fix/linux/debian-cve-2026-33278.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 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 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 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 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 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 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 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 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 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 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 |

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Data as of 2026-11-09T07:25:28Z 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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