# CVE-2026-40211: dnsdist: An attacker can send crafted DNS over HTTP/3 queries, triggering an exception that prevents some buffer from being fr...

CVE-2026-40211 is fixed in dnsdist on 1 platform, first by DEBIAN-CVE-2026-40211, released June 26, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-40211
- Priority: Routine
- CVSS: 5.3 (medium)
- EPSS: 0.0070
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 25, 2026

## Description

An attacker can send crafted DNS over HTTP/3 queries, triggering an exception that prevents some buffer from being freed right away. The buffer will be freed at the end of the QUIC connection, but on some setups it might be possible to open enough concurrent DoH3 streams to trigger an out-of-memory condition, resulting in a denial of service.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | dnsdist Debian 13.5 (trixie) | 1.9.15-0+deb13u1 | [DEBIAN-CVE-2026-40211](https://patchblox.com/security/data/fix/linux/debian-cve-2026-40211.md) | Jun 26, 2026 |
| Linux | dnsdist Debian 14 | 2.1.0-1 | [DEBIAN-CVE-2026-40211](https://patchblox.com/security/data/fix/linux/debian-cve-2026-40211.md) | Jun 26, 2026 |
| Linux | dnsdist opensuse-leap 16.0 | 1.9.15-160000.1.1 | [OPENSUSE-SU-2026:21533-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21533-1.md) | Aug 5, 2026 |
| Linux | dnsdist sles 16.0 | 1.9.15-160000.1.1 | [SUSE-SU-2026:23146-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23146-1.md) | Aug 5, 2026 |

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Data as of 2026-11-08T00:53:09Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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