CVE-2026-39155

6.5 MEDIUM 0.2% exploit odds No fix listed Denial of service

What it is

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.

At a glance

Exploitability: Can be exploited over the network with a low-privilege account. High risk of service disruption.
Exploit odds: 0.2% chance of exploitation in the next 30 days (EPSS).
Fix: No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

2026-07-23 21:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-07-30 19:32 UTC Last updatedMost recent change to the record

Details

Published: 2026-07-23 21:17 UTC
Last modified: 2026-07-30 19:32 UTC
Exploit probability: 0.2% · EPSS, next 30 days
Weakness: CWE-345
Record status: Deferred

Attack profile CVSS 3.1 · 6.5

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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References

NVD record · CVE.org record