Denial of Service Vulnerability in PowerDNS Backend Connections
CVE-2026-40209

5.3MEDIUM

Key Information:

Vendor

Powerdns

Status
Dnsdist
Vendor
CVE Published:
25 June 2026

What is CVE-2026-40209?

A denial of service issue in PowerDNS allows attackers to send IXFR queries that can cause outgoing TCP connections to a backend to become unresponsive until a timeout occurs. This can result in service disruptions for users, particularly if there is a limit on concurrent connections or if file descriptors are exhausted.

Affected Version(s)

DNSdist 1.9.0 < 1.9.15

DNSdist 2.0.0 < 2.0.7

References

https://www.dnsdist.org/security-advisories/powerdns-advi...

CVSS V3.1

Score:
5.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Qifan Zhang (Palo Alto Networks)
.