Quick answers
- Is CVE-2026-19401 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-19401 being exploited in the wild.
- How severe is CVE-2026-19401?
- High severity, with a CVSS score of 7.5, published 26 August 2026.
- Which products and versions are affected?
- Nlnetlabs Nsd 4.3.7 through 4.15.0.
- Is there a fix for CVE-2026-19401?
- A patch was published on 2026-08-26: Version 4.15.1 released with patch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-19401 attacked?
- It is attacked over the network, in a hosted service.
- Am I affected by CVE-2026-19401?
- Check whether you run Nlnetlabs Nsd at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
This is a denial-of-service vulnerability triggered by improper handling of DNS Cookie EDNS options. An unauthenticated remote attacker can send a crafted DNS query with a specially tuned number of DNS Cookie options (e.g., 17 when UDP payload size is 512) to crash NSD child processes, particularly in debug/non-release builds. The vulnerability is triggered over the network without authentication or user interaction. By continuously sending such queries, an attacker positioned close to the target can severely hamper or deny all DNS service. NSD versions 4.3.7 through 4.15.0 are affected; version 4.15.1 includes a patch, and a manual patch is available for 4.15.0.
Affected products
- NLnetLabs NSD 4.3.7 through 4.15.0
Timeline
- 2026-08-26: disclosed
- 2026-08-26: patched: Version 4.15.1 released with patch