What’s Vulnerable › Vulnerabilities
CVE-2026-35501: Bypass of a configured island trust anchor underneath an insecure parent from an atacker-controlled NSEC record.
- Severity: low (CVSS 3.7 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.1% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-10-21 · updated 2026-10-29
- Weakness: CWE-354
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.
Affected products
- NLnet Labs Unbound: from 1.0.1 before 1.26.2 — fixed in 1.26.2
How to fix
Upgrade to a fixed version: NLnet Labs Unbound 1.26.2. Check the vendor advisory for mitigations.
References
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