CVE-2026-42960

DNS cache poisoning via non-NS authority RRSets

Published May 20, 2026 · Updated May 20, 2026

DNS cache poisoning in NLnet Labs Unbound 1.25.0 and earlier allows attackers to redirect resolution via forged DNS replies. Unbound trusts address records from the additional section when they accompany a non-NS authority RRSet that has in-zone delegation trust, then stores those addresses in its cache. Exploitation requires reply spoofing or fragmentation, and poisoned entries can make subsequent clients resolve affected names to attacker-selected addresses.

CVSS severity10.0
Critical
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

DNS cache poisoning in NLnet Labs Unbound 1.25.0 and earlier allows attackers to redirect resolution via forged DNS replies. Unbound trusts address records from the additional section when they accompany a non-NS authority RRSet that has in-zone delegation trust, then stores those addresses in its cache. Exploitation requires reply spoofing or fragmentation, and poisoned entries can make subsequent clients resolve affected names to attacker-selected addresses.

The record

CVE
CVE-2026-42960
Published
May 20, 2026
Updated
May 20, 2026
Vendor
NLnet Labs
Product
Unbound
Classifications
CWE-349, T1557
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 20, 2026CVE publishedPublication date reported by the CVE source.
  2. May 20, 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 <1.25.1

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

NLnet Labs · Unboundversion=0 <1.25.1

Published CVSS scores

10.0NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H
5.7NLnet LabsCVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:H/E:P

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-349Acceptance of Extraneous Untrusted Data With Trusted Data
T1557Adversary-in-the-Middle

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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