# CVE-2019-19331: knot-resolver: knot-resolver before version 4.3.0 is vulnerable to denial of service through high CPU utilization

CVE-2019-19331 is fixed in 2 products on 1 platform, first by knot-resolver 3.2.1-3ubuntu2.2, released May 19, 2020. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2019-19331
- Priority: Routine
- CVSS: n/a (Medium)
- EPSS: 0.0211
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Dec 16, 2019

## Description

knot-resolver before version 4.3.0 is vulnerable to denial of service through high CPU utilization. DNS replies with very many resource records might be processed very inefficiently, in extreme cases taking even several CPU seconds for each such uncached message. For example, a few thousand A records can be squashed into one DNS message (limit is 64kB).

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | knot-resolver Ubuntu 20.04 LTS (focal) | 3.2.1-3ubuntu2.2 | [knot-resolver 3.2.1-3ubuntu2.2](https://patchblox.com/security/data/fix/linux/ubuntu-focal-knot-resolver-3.2.1-3ubuntu2.2.md) | May 19, 2020 |
| Linux | knot-resolver-module-http Ubuntu 20.04 LTS (focal) | 3.2.1-3ubuntu2.2 | [knot-resolver-module-http 3.2.1-3ubuntu2.2](https://patchblox.com/security/data/fix/linux/ubuntu-focal-knot-resolver-module-http-3.2.1-3ubuntu2.2.md) | May 19, 2020 |

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Data as of 2026-11-07T06:34:28Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo