CVE-2026-39155

Published Jul 23, 2026 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Title Incorrect NSEC Calculation Leading to Authenticated Denial Interval and Resolver DoS
Type Values Removed Values Added
Title Incorrect NSEC Calculation Leading to Authenticated Denial Interval and Resolver DoS
Type Values Removed Values Added
Title Incorrect NSEC Owner Computation in Knot DNS Leading to Denial of Service
Type Values Removed Values Added
Title Incorrect NSEC Owner Computation in Knot DNS Leading to Denial of Service
Type Values Removed Values Added
Weaknesses CWE-345
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Knot-dns
Knot-dns knot Dns
Vendors & Products Knot-dns
Knot-dns knot Dns
Type Values Removed Values Added
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.
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
mitre
Published
Updated
Jul 24, 2026, 7:35 PM
Reserved
Apr 6, 2026, 12:00 AM
Status
Deferred
Published
Jul 23, 2026, 9:17 PM
Modified
Jul 30, 2026, 7:32 PM