CVE-2026-39155: n/a
Knot DNS before 3.4.10 and 3.5.x before 3.5.4 contains a vulnerability in mod-onlinesign where the next NSEC owner name can be computed incorrectly. This can create an overly broad authenticated denial interval, allowing downstream validating resolvers using aggressive negative caching to synthesize negative answers for legitimate names and causing resolver-side denial of service.
AI Analysis
Technical Summary
The vulnerability in Knot DNS's mod-onlinesign module affects versions prior to 3.4.10 and 3.5.4. It involves incorrect computation of the next NSEC owner name, causing an overly broad authenticated denial interval. This can mislead downstream validating DNS resolvers employing aggressive negative caching to synthesize negative DNS answers for valid domain names, effectively causing denial of service at the resolver level.
Potential Impact
Downstream validating DNS resolvers that rely on aggressive negative caching may incorrectly treat legitimate domain names as non-existent due to the overly broad denial interval. This results in denial of service conditions on those resolvers, potentially disrupting DNS resolution for end users relying on affected resolvers.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, consider disabling or limiting aggressive negative caching on downstream validating resolvers as a temporary mitigation.
CVE-2026-39155: n/a
Description
Knot DNS before 3.4.10 and 3.5.x before 3.5.4 contains a vulnerability in mod-onlinesign where the next NSEC owner name can be computed incorrectly. This can create an overly broad authenticated denial interval, allowing downstream validating resolvers using aggressive negative caching to synthesize negative answers for legitimate names and causing resolver-side denial of service.
Affected software
pkg:github/cz-nic/knot-dnsRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in Knot DNS's mod-onlinesign module affects versions prior to 3.4.10 and 3.5.4. It involves incorrect computation of the next NSEC owner name, causing an overly broad authenticated denial interval. This can mislead downstream validating DNS resolvers employing aggressive negative caching to synthesize negative DNS answers for valid domain names, effectively causing denial of service at the resolver level.
Potential Impact
Downstream validating DNS resolvers that rely on aggressive negative caching may incorrectly treat legitimate domain names as non-existent due to the overly broad denial interval. This results in denial of service conditions on those resolvers, potentially disrupting DNS resolution for end users relying on affected resolvers.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, consider disabling or limiting aggressive negative caching on downstream validating resolvers as a temporary mitigation.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mitre
- Date Reserved
- 2026-04-06T00:00:00.000Z
- Cvss Version
- null
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a62781b9c2644c7f8a7dd7c
Added to database: 07/23/2026, 20:22:51 UTC
Last enriched: 07/23/2026, 20:37:48 UTC
Last updated: 07/23/2026, 21:01:31 UTC
Views: 4
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