CVE-2026-42255Network attack vector

Traffic amplification via cyclic name server delegation

Published Apr 26, 2026 · Updated Apr 26, 2026

DNS traffic amplification in Technitium DNS Server before 15.0 allows remote attackers to amplify traffic via cyclic name-server delegation. The upstream release notes identify cyclic delegation as the trigger but do not disclose the resolver function or incorrect processing step. Unauthenticated access to recursive DNS resolution is sufficient, and the amplified traffic can degrade a third-party target's availability.

CVSS severity7.2
High
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

DNS traffic amplification in Technitium DNS Server before 15.0 allows remote attackers to amplify traffic via cyclic name-server delegation. The upstream release notes identify cyclic delegation as the trigger but do not disclose the resolver function or incorrect processing step. Unauthenticated access to recursive DNS resolution is sufficient, and the amplified traffic can degrade a third-party target's availability.

The record

CVE
CVE-2026-42255
Published
Apr 26, 2026
Updated
Apr 26, 2026
Vendor
Technitium
Product
Technitium DNS Server
Classifications
CWE-684, T1498.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 26, 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=0 <15.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Technitium · Technitium DNS Serverversion=0 <15.0.0

Published CVSS scores

7.2MITRECVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:L
6.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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-684Incorrect Provision of Specified Functionality
T1498.002Network Denial of Service: Reflection Amplification

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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