CVE-2026-77955Network attack vectorHinoki check available

Tampered zone serving via deferred ZONEMD verification

Published Sep 16, 2026 · Updated Sep 16, 2026

ZONEMD verification bypass in NLnet Labs Unbound 1.13.2 through 1.26.1 allows attackers to serve tampered zone data. For configured zones below a trust anchor, asynchronous DS and DNSKEY resolution lets contents be served or written before the ZONEMD check completes. The flaw requires zonemd-check: yes; with zonefile enabled, failed data persists on disk and is reloaded at startup until verification fails again.

CVSS severityUnavailable
Unscored
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

ZONEMD verification bypass in NLnet Labs Unbound 1.13.2 through 1.26.1 allows attackers to serve tampered zone data. For configured zones below a trust anchor, asynchronous DS and DNSKEY resolution lets contents be served or written before the ZONEMD check completes. The flaw requires zonemd-check: yes; with zonefile enabled, failed data persists on disk and is reloaded at startup until verification fails again.

The record

CVE
CVE-2026-77955
Published
Sep 16, 2026
Updated
Sep 16, 2026
Vendor
NLnet Labs
Product
Unbound
Classifications
Unavailable
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Sep 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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=1.13.2 <1.26.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

NLnet Labs · Unboundversion=1.13.2 <1.26.1

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

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

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

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Technologies

Your stack

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Your stack

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