CVE-2026-78227Network attack vectorHinoki check available

Remote resolver crash via stale DoQ retransmission pointer

Published Sep 16, 2026 · Updated Sep 16, 2026

Use-after-free in NLnet Labs Unbound 1.22.0 through 1.26.0 allows remote attackers to crash the resolver through a DoQ stream reset. A client RESET_STREAM frees the stream output buffer while ngtcp2 retains shallow retransmission pointers, and the next PTO copies from freed memory. Exposure requires a build made with --with-libngtcp2 and a configured quic-port; withholding acknowledgments and spraying about 20 queries causes an abnormal server exit.

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

Use-after-free in NLnet Labs Unbound 1.22.0 through 1.26.0 allows remote attackers to crash the resolver through a DoQ stream reset. A client RESET_STREAM frees the stream output buffer while ngtcp2 retains shallow retransmission pointers, and the next PTO copies from freed memory. Exposure requires a build made with --with-libngtcp2 and a configured quic-port; withholding acknowledgments and spraying about 20 queries causes an abnormal server exit.

The record

CVE
CVE-2026-78227
Published
Sep 16, 2026
Updated
Sep 16, 2026
Vendor
NLnet Labs
Product
Unbound
Classifications
T1499.004
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=1.22.0 <1.26.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

NLnet Labs · Unboundversion=1.22.0 <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 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

T1499.004Endpoint Denial of Service: Application or System Exploitation

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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