CVE-2026-40209Network attack vector

Denial of service via malformed IXFR SOA

Published Jun 25, 2026 · Updated Jun 25, 2026

Resource exhaustion in PowerDNS DNSdist 1.9.0 through 1.9.14 and 2.0.0 through 2.0.6 allows remote attackers to interrupt DNS service. When malformed SOA parsing raises an exception during IXFR handling, the TCP downstream handler retains its outgoing backend connection until timeout. Repeated unauthenticated queries exhaust a backend connection limit or the process's file descriptors, interrupting proxied DNS requests without enabling system compromise.

CVSS severity5.3
Medium
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in PowerDNS DNSdist 1.9.0 through 1.9.14 and 2.0.0 through 2.0.6 allows remote attackers to interrupt DNS service. When malformed SOA parsing raises an exception during IXFR handling, the TCP downstream handler retains its outgoing backend connection until timeout. Repeated unauthenticated queries exhaust a backend connection limit or the process's file descriptors, interrupting proxied DNS requests without enabling system compromise.

The record

CVE
CVE-2026-40209
Published
Jun 25, 2026
Updated
Jun 25, 2026
Vendor
PowerDNS
Product
DNSdist
Classifications
CWE-772, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.9.0 <1.9.15
  2. Affected versionversion=2.0.0 <2.0.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

PowerDNS · DNSdistversion=1.9.0 <1.9.15; version=2.0.0 <2.0.7

Published CVSS scores

5.3Open-XchangeCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-772Missing Release of Resource after Effective Lifetime
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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