# CVE-2026-35501: unbound: When NLnet Labs Unbound 1.0.1 up to and including version 1.26.1 is configured with both a root trust anchor and an a...

CVE-2026-35501 is fixed in 12 products on 1 platform, first by DEBIAN-CVE-2026-35501, released October 24, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-35501
- Priority: Routine
- CVSS: 3.7 (low)
- EPSS: 0.0011
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 21, 2026

## Description

When NLnet Labs Unbound 1.0.1 up to and including version 1.26.1 is configured with both a root trust anchor and an additional 'trust-anchor:' for an island-of-security zone whose parent is provably insecure under the root chain, a malicious actor with a forged NSEC reply with the SOA bit cleared can trick Unbound to treat the configured trust island as insecure. This happens because the DNSSEC validator in Unbound accepts and caches the NSEC insecure response bypassing the RRSIG validation that the validator was supposed to do. The acceptance of the NSEC record at the trust anchor apex was allowed due to and old fix for type DS and NSEC queries from clients when trust anchor for that name existed.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | python3-unbound amzn 2023 | 1.17.1-1.amzn2023.0.17 | [ALAS2023-2026-3313](https://patchblox.com/security/data/fix/linux/alas2023-2026-3313.md) | Nov 7, 2026 |
| Linux | python3-unbound-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.17 | [ALAS2023-2026-3313](https://patchblox.com/security/data/fix/linux/alas2023-2026-3313.md) | Nov 7, 2026 |
| Linux | unbound Debian 13.5 (trixie) | 1.26.2-0+deb13u1 | [DEBIAN-CVE-2026-35501](https://patchblox.com/security/data/fix/linux/debian-cve-2026-35501.md) | Oct 24, 2026 |
| Linux | unbound Debian 14 | 1.26.2-1 | [DEBIAN-CVE-2026-35501](https://patchblox.com/security/data/fix/linux/debian-cve-2026-35501.md) | Oct 24, 2026 |
| Linux | unbound amzn 2023 | 1.17.1-1.amzn2023.0.17 | [ALAS2023-2026-3313](https://patchblox.com/security/data/fix/linux/alas2023-2026-3313.md) | Nov 7, 2026 |
| Linux | unbound-anchor amzn 2023 | 1.17.1-1.amzn2023.0.17 | [ALAS2023-2026-3313](https://patchblox.com/security/data/fix/linux/alas2023-2026-3313.md) | Nov 7, 2026 |
| Linux | unbound-anchor-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.17 | [ALAS2023-2026-3313](https://patchblox.com/security/data/fix/linux/alas2023-2026-3313.md) | Nov 7, 2026 |
| Linux | unbound-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.17 | [ALAS2023-2026-3313](https://patchblox.com/security/data/fix/linux/alas2023-2026-3313.md) | Nov 7, 2026 |
| Linux | unbound-debugsource amzn 2023 | 1.17.1-1.amzn2023.0.17 | [ALAS2023-2026-3313](https://patchblox.com/security/data/fix/linux/alas2023-2026-3313.md) | Nov 7, 2026 |
| Linux | unbound-devel amzn 2023 | 1.17.1-1.amzn2023.0.17 | [ALAS2023-2026-3313](https://patchblox.com/security/data/fix/linux/alas2023-2026-3313.md) | Nov 7, 2026 |
| Linux | unbound-libs amzn 2023 | 1.17.1-1.amzn2023.0.17 | [ALAS2023-2026-3313](https://patchblox.com/security/data/fix/linux/alas2023-2026-3313.md) | Nov 7, 2026 |
| Linux | unbound-libs-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.17 | [ALAS2023-2026-3313](https://patchblox.com/security/data/fix/linux/alas2023-2026-3313.md) | Nov 7, 2026 |
| Linux | unbound-utils amzn 2023 | 1.17.1-1.amzn2023.0.17 | [ALAS2023-2026-3313](https://patchblox.com/security/data/fix/linux/alas2023-2026-3313.md) | Nov 7, 2026 |
| Linux | unbound-utils-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.17 | [ALAS2023-2026-3313](https://patchblox.com/security/data/fix/linux/alas2023-2026-3313.md) | Nov 7, 2026 |

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Data as of 2026-11-08T00:53:09Z 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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