CVE-2026-40209 PUBLISHED

Denial of service via IXFR queries

Assigner: OX
Reserved: 10.04.2026 Published: 25.06.2026 Updated: 25.06.2026

An attacker might be able to cause outgoing TCP connections to backend to be stuck until a timeout occurs instead of being released immediately, by sending IXFR queries. This could be used to cause a denial of service if there is a limit to the number of concurrent connections to this backend, or if the process runs out of file descriptors.

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CVSS Score: 5.3

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	None
Privileges Required	None	Integrity Impact	None
User Interaction	None	Availability Impact	Low

CVSS 3.1

Product Status

Vendor	PowerDNS
Product	DNSdist
Versions	Default: unaffected affected from 1.9.0 to 1.9.15 (excl.) affected from 2.0.0 to 2.0.7 (excl.)

Credits

Qifan Zhang (Palo Alto Networks) finder

References

https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-09.html

Problem Types

Missing Release of Resource after Effective Lifetime CWE