Vulnerability · CVE-2026-35501
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
Published Oct 21, 2026 · catalog updated Oct 23, 2026 · When NLnet Labs Unbound
Last checked Nov 3, 2026. A connected source was read within the last 7 days.
Check if you run it
No confirmed exploitation is on record for CVE-2026-35501. EPSS is 0.11%. Act only if a listed version of When NLnet Labs Unbound is installed.
Gaps on this record
- The stored product name is a package slug. The name on this page is taken from the title (When NLnet Labs Unbound).
- No vendor fix or required action is stored. Compare the linked advisory before you change production.
- Severity
- Low3.7
- Known exploitation
- Not in CISA/VulnCheck KEV
- EPSS
- 0.11%
- Remediation
- Advisory link
- Affected products
- Debian:12 unbound · Debian:13 unbound · Debian:14 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 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.
Are you affected?
Enter the version you run. The result uses only the ranges stored on this record.
The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.
- Debian:12 unbound1.17.1-2, 1.17.1-2+deb12u1, 1.17.1-2+deb12u2
- Debian:13 unbound0 → 1.26.2-0+deb13u1
- Debian:14 unbound1.22.0-2, 1.23.1-1, 1.24.0-1
How to fix CVE-2026-35501
Upgrade
CVE-2026-35501 lists a fix boundary at 1.26.2-0+deb13u1. Compare the installed build with that boundary before you change production.
Version check
Fixed in 1.26.2-0+deb13u1 · 6 other ranges on the advisory
Advisory
Open the cve_org record and follow its fix.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
No confirmed exploitation is on record for CVE-2026-35501. EPSS is 0.11%. Act only if a listed version of When NLnet Labs Unbound is installed.
Which versions are affected?
Compare what you have installed with 1.17.1-2, 1.17.1-2+deb12u1, 1.17.1-2+deb12u2, 0 → 1.26.2-0+deb13u1, 1.22.0-2, 1.23.1-1, 1.24.0-1. Compare the installed version with the linked vendor advisory before you change production.
What should an analyst verify?
CWE-354. EPSS 0.11%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Technology hubs
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Oct 21, 2026 · NIST NVD
Detected
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 va
Oct 22, 2026 · NIST NVD
Updated
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 va
Oct 23, 2026 · Trivy Vulnerability DB
Fix available
unbound fixed in 1.26.2-0+deb13u1
Oct 23, 2026 · Trivy Vulnerability DB
Fix available
unbound fixed in 1.26.2-0+deb13u1
Oct 23, 2026 · Trivy Vulnerability DB
Updated
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 va
Sources
- CVE.orgVulnerability recordCVE-2026-35501
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2026-35501
30-day exploitation probability 0.11%
first.org - NIST NVDVulnerability recordCVE-2026-35501
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 th
nvd.nist.gov - Trivy Vulnerability DBPackage advisoryDEBIAN-CVE-2026-35501
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 th
osv.dev
References
Freshness
Last verified in this catalog Nov 3, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.
- FIRST EPSSOct 31, 2026
- Trivy Vulnerability DBOct 23, 2026
- NIST NVDOct 22, 2026
- CVE.orgOct 21, 2026