# CVE-2026-40208: PowerDNS DNSdist denial of service in DoH3 queries

Source: https://junglewise.ai/threats/cve-2026-40208-powerdns-dnsdist-denial-of-service-in-doh3-queries  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-25. Updated: 2026-06-25  
License: CC BY 4.0 with a link back

CVE-2026-40208 · Severity: low · CVSS 3.7 · Published 2026-06-25

PowerDNS DNSdist, a tool used to balance and manage internet traffic for domain name systems, contains a flaw in how it handles modern DNS-over-HTTP/3 (DoH3) requests. An attacker can send specially formatted requests that cause delays in how the system processes legitimate traffic. While this does not expose data, it can slow down the responsiveness of the DNS service for users.

Technologies: [Powerdns Dnsdist](https://junglewise.ai/threats/technologies/dnsdist). Vendors: [Powerdns](https://junglewise.ai/threats/vendors/powerdns).

## Quick answers

**Is CVE-2026-40208 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-40208 being exploited in the wild.

**How severe is CVE-2026-40208?** Low severity, with a CVSS score of 3.7, published 25 June 2026.

**Which products and versions are affected?** Powerdns Dnsdist 1.9.0 to 1.9.14, 2.0.0 to 2.0.6.

**Is there a fix for CVE-2026-40208?** A patch was published on 2026-06-25: Fixed in versions 1.9.15 and 2.0.7 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-40208 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-40208?** Check whether you run Powerdns Dnsdist 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

A vulnerability exists in the DNS-over-HTTP/3 (DoH3) implementation of PowerDNS DNSdist (specifically within doh3.cc). The issue is triggered when an attacker sends DoH3 GET queries containing an invalid DATA frame. This can lead to a delay in the processing of subsequent DoH3 queries, resulting in a partial denial of service. The attack is network-reachable and requires no authentication, though it has a high attack complexity. The vulnerability is addressed in DNSdist versions 1.9.15 and 2.0.7. Organizations unable to upgrade can mitigate the risk by disabling DoH3 support.

## Affected products

- PowerDNS DNSdist 1.9.0 to 1.9.14, 2.0.0 to 2.0.6

## Timeline

- 2026-04-13: disclosed: Discovery date
- 2026-06-25: advisory: PowerDNS Security Advisory 2026-09 published
- 2026-06-25: patched: Fixed in versions 1.9.15 and 2.0.7

## References

- [https://repo.powerdns.com/](https://repo.powerdns.com/)
- [https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-09.html](https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-09.html)

## Related threats

- [PowerDNS DNSdist EDNS options smuggling in EDNS processing](https://junglewise.ai/threats/cve-2026-42004-powerdns-dnsdist-edns-options-smuggling-in-edns-processing)
- [PowerDNS DNSdist denial of service in DNS over HTTP/3](https://junglewise.ai/threats/cve-2026-40211-powerdns-dnsdist-denial-of-service-in-dns-over-http-3)
- [PowerDNS DNSdist out-of-bounds read in SetMacAddrAction](https://junglewise.ai/threats/cve-2026-40210-powerdns-dnsdist-out-of-bounds-read-in-setmacaddraction)
- [PowerDNS DNSdist denial of service via IXFR queries](https://junglewise.ai/threats/cve-2026-40209-powerdns-dnsdist-denial-of-service-via-ixfr-queries)
- [PowerDNS DNSdist denial of service in Prometheus endpoint](https://junglewise.ai/threats/cve-2026-40011-powerdns-dnsdist-denial-of-service-in-prometheus-endpoint)