CVE-2026-35501
LOWDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 1% of all known CVEs.
References
Related Vulnerabilities
Other CWE-354 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-48795 | Medium | 5.9 | 94% | - | Fix |
| CVE-2019-1166 | Medium | 5.9 | 68% | - | - |
| CVE-2024-3596 | Critical | 9.0 | 15% | - | Fix |
| CVE-2020-26141 | Medium | 6.5 | 3.1% | - | Fix |
| CVE-2020-25862 | High | 7.5 | 2.4% | - | Fix |
| CVE-2023-38802 | High | 7.5 | 1.8% | - | Fix |
Common questions
How do I fix CVE-2026-35501?
Upgrade unbound on debian 13 to 1.26.2-0+deb13u1 or later.
Is CVE-2026-35501 being actively exploited?
Not that we know of. CVE-2026-35501 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.11% is the estimated probability that it will be exploited in the next 30 days. That is higher than 1% of all scored CVEs.
How severe is CVE-2026-35501?
CVE-2026-35501 has a CVSS v3 base score of 3.7, rated low. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-35501 affect?
Published advisories record a fix for unbound (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
Embed a live status badge for CVE-2026-35501
Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-10-29.