CVE-2026-77860Network attack vectorHinoki check available

Pulsing DoS amplification via double counter decrement

Published Sep 16, 2026 · Updated Sep 16, 2026

Denial of service in NLnet Labs Unbound 1.20.0 through 1.26.0 allows remote attackers to amplify pulsing DNS traffic. The serve-expired reply path decrements the per-client wait-limit counter twice for a pump query, canceling the accounting effect of a preceding unanswered slow query. Exploitation requires control of an authoritative zone with short TTLs and query access to the resolver; alternating slow and pump queries can occupy the global mesh quota.

CVSS severityUnavailable
Unscored
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Denial of service in NLnet Labs Unbound 1.20.0 through 1.26.0 allows remote attackers to amplify pulsing DNS traffic. The serve-expired reply path decrements the per-client wait-limit counter twice for a pump query, canceling the accounting effect of a preceding unanswered slow query. Exploitation requires control of an authoritative zone with short TTLs and query access to the resolver; alternating slow and pump queries can occupy the global mesh quota.

The record

CVE
CVE-2026-77860
Published
Sep 16, 2026
Updated
Sep 16, 2026
Vendor
NLnet Labs
Product
Unbound
Classifications
T1499.002
Attack vector
network
Privileges
unauthenticated

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=1.20.0 <1.26.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

NLnet Labs · Unboundversion=1.20.0 <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

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

Weakness, pattern, technique

T1499.002Endpoint Denial of Service: Service Exhaustion Flood

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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