CVE-2026-42004Network attack vector

Security-rule bypass via malformed OPT record rewriting

Published Jun 25, 2026 · Updated Jun 25, 2026

Security-rule bypass in PowerDNS DNSdist 1.9.0 through 1.9.14 and 2.0.0 through 2.0.6 allows remote attackers to smuggle EDNS options. The EDNS parser ignores a malformed OPT record during filtering, but ECS insertion rewrites it as valid before forwarding, so prohibited options reach the backend. The flaw is reachable without authentication when EDNS Client Subnet insertion is enabled and EDNS option filtering is trusted; impact is limited to backend-visible option integrity.

CVSS severity3.7
Low
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Security-rule bypass in PowerDNS DNSdist 1.9.0 through 1.9.14 and 2.0.0 through 2.0.6 allows remote attackers to smuggle EDNS options. The EDNS parser ignores a malformed OPT record during filtering, but ECS insertion rewrites it as valid before forwarding, so prohibited options reach the backend. The flaw is reachable without authentication when EDNS Client Subnet insertion is enabled and EDNS option filtering is trusted; impact is limited to backend-visible option integrity.

The record

CVE
CVE-2026-42004
Published
Jun 25, 2026
Updated
Jun 25, 2026
Vendor
PowerDNS
Product
DNSdist
Classifications
CWE-115
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

3.7Open-XchangeCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

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.

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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-115Misinterpretation of Input

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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