# CVE-2026-77955: unbound: In NLnet Labs Unbound 1.13.2 up to and including 1.26.1, a vulnerability in ZONEMD configured zones (zonemd-check: ye...

CVE-2026-77955 is fixed in 12 products on 1 platform, first by DEBIAN-CVE-2026-77955, released September 19, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-77955
- Priority: Routine
- CVSS: 4.4 (medium)
- EPSS: 0.0017
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 16, 2026

## Description

In NLnet Labs Unbound 1.13.2 up to and including 1.26.1, a vulnerability in ZONEMD configured zones (zonemd-check: yes) which are located below (but not at) a trust anchor allow for an attack window where (tampered with) zone contents are served (or stored to disk) prior to the ZONEMD integrity check. This is caused by the needed DS/DNSKEY asynchronous resolution that needs to happen before the ZONEMD check completes. If a zonefile is written to disk (zonefile: option) while the ZONEMD check failed, the tampered data are reloaded on startup and available until ZONEMD verification concludes again. If verification fails, the data is not served any more but still persists on disk for future reloads.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | python3-unbound amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 |
| Linux | python3-unbound-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 |
| Linux | unbound Debian 13.5 (trixie) | 1.26.1-0+deb13u1 | [DEBIAN-CVE-2026-77955](https://patchblox.com/security/data/fix/linux/debian-cve-2026-77955.md) | Sep 19, 2026 |
| Linux | unbound Debian 14 | 1.26.1-1 | [DEBIAN-CVE-2026-77955](https://patchblox.com/security/data/fix/linux/debian-cve-2026-77955.md) | Sep 19, 2026 |
| Linux | unbound amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 |
| Linux | unbound opensuse-leap 16.0 | 1.26.1-160000.1.1 | [OPENSUSE-SU-2026:22082-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-22082-1.md) | Nov 7, 2026 |
| Linux | unbound sles 15.6 | 1.26.1-150600.23.24.1 | [SUSE-SU-2026:4620-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4620-1.md) | Nov 7, 2026 |
| Linux | unbound sles 15.7 | 1.26.1-150600.23.24.1 | [SUSE-SU-2026:4620-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4620-1.md) | Nov 7, 2026 |
| Linux | unbound sles 16.0 | 1.26.1-160000.1.1 | [SUSE-SU-2026:24226-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-24226-1.md) | Nov 7, 2026 |
| Linux | unbound-anchor amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 |
| Linux | unbound-anchor-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 |
| Linux | unbound-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 |
| Linux | unbound-debugsource amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 |
| Linux | unbound-devel amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 |
| Linux | unbound-libs amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 |
| Linux | unbound-libs-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 |
| Linux | unbound-utils amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 |
| Linux | unbound-utils-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 |

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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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