CVE-2026-39155
MediumCVSS 6.5Exploitation Probability (EPSS)
Low risk5th percentile - higher than 5% of all known CVEs
Summary
In Knot DNS before versions 3.4.10 and 3.5.4, the mod-onlinesign module incorrectly computes the next NSEC owner name, creating an overly broad authenticated denial interval. This allows downstream resolvers using aggressive negative caching to synthesize negative answers for legitimate names, causing resolver-side denial of service.
Risk Assessment
An attacker can exploit this to block access to legitimate domains, causing denial of service for end users relying on resolvers with aggressive negative caching.
Recommendation
Upgrade Knot DNS to version 3.4.10 or later (for 3.4.x branch) or 3.5.4 or later (for 3.5.x branch).
Other vulnerabilities in Knot DNS
Original NVD description (English source)
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.