CVE-2026-40209

Denial of service via IXFR queries

Published Jun 25, 2026 CVSS 3.1 · 5.3 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DSA Debian DSA DSA-6367-1 dnsdist security update
History
Type Values Removed Values Added
First Time appeared Powerdns
Powerdns dnsdist
Vendors & Products Powerdns
Powerdns dnsdist
Type Values Removed Values Added
Weaknesses CWE-400
Type Values Removed Values Added
Weaknesses CWE-400
Type Values Removed Values Added
Weaknesses CWE-772
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Denial of service via IXFR queries
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
OX
Published
Updated
Jun 25, 2026, 1:56 PM
Reserved
Apr 10, 2026, 7:11 AM
Status
Deferred
Published
Jun 25, 2026, 1:16 PM
Modified
Oct 25, 2026, 11:10 PM