CVE-2026-40209 Details
Description
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.
A denial-of-service vulnerability has been identified in PowerDNS DNSdist versions through 2.0.6 and 1.9.14. The issue arises when an attacker sends crafted IXFR queries, causing outgoing TCP connections to the backend to become stuck until a timeout occurs, rather than being released immediately. This can lead to a denial-of-service condition, especially if there is a limit on concurrent connections to the backend or if the process exhausts available file descriptors.
Users can upgrade to PowerDNS DNSdist versions 1.9.15 or 2.0.7, or block incoming IXFR queries by adding a specific action to refuse those queries.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Jun 25, 2026CISA-ADP
Assessed Jun 25, 2026References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-09.html | [email protected] | AdvisoryBundleRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-772 | Missing Release of Resource after Effective Lifetime | CISA-ADP |
Affected Products
| Product | Versions |
|---|---|
| PowerDNS DNSdist | <= 2.0.6 (semver) <= 1.9.14 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 25, 2026 | CVE Modified | CISA-ADP |
| Jun 25, 2026 | New CVE Received | [email protected] |