Resolver denial of service via incorrect NSEC interval
Published Jul 23, 2026 · Updated Jul 23, 2026
Denial of service in Knot DNS before 3.4.10 and 3.5.x before 3.5.4 allows remote attackers to suppress legitimate DNS answers via queries. The mod-onlinesign module computes an incorrect next NSEC owner name and signs an interval that covers names outside the intended denial range. Exposure requires mod-onlinesign and a downstream validating resolver using aggressive negative caching; legitimate names can then resolve as nonexistent.
Summary
What happened
Denial of service in Knot DNS before 3.4.10 and 3.5.x before 3.5.4 allows remote attackers to suppress legitimate DNS answers via queries. The mod-onlinesign module computes an incorrect next NSEC owner name and signs an interval that covers names outside the intended denial range. Exposure requires mod-onlinesign and a downstream validating resolver using aggressive negative caching; legitimate names can then resolve as nonexistent.
The record
- CVE
- CVE-2026-39155
- Published
- Jul 23, 2026
- Updated
- Jul 23, 2026
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-345
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 23, 2026CVE publishedPublication date reported by the CVE source.
- Jul 23, 2026Record updatedLatest update available in the CVE record.
Exploitability
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