CVE-2026-82717Network attack vector

Remote code execution via CNAME heap overflow

Published Sep 16, 2026 · Updated Sep 16, 2026

Heap buffer overflow in NLnet Labs Unbound 1.26.0 and earlier allows remote attackers to crash the resolver or execute code. During CNAME synthesis, max-TTL rewriting overwrites a value referenced by a compression pointer; the resulting error path fails to advance the packet-buffer position and writes past the heap buffer. Exploitation requires a crafted upstream response and favorable heap layout; the bounded result is resolver crash, with code execution limited to specific systems and compilation options.

CVSS severityUnavailable
Unscored
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in NLnet Labs Unbound 1.26.0 and earlier allows remote attackers to crash the resolver or execute code. During CNAME synthesis, max-TTL rewriting overwrites a value referenced by a compression pointer; the resulting error path fails to advance the packet-buffer position and writes past the heap buffer. Exploitation requires a crafted upstream response and favorable heap layout; the bounded result is resolver crash, with code execution limited to specific systems and compilation options.

The record

CVE
CVE-2026-82717
Published
Sep 16, 2026
Updated
Sep 16, 2026
Vendor
NLnet Labs
Product
Unbound
Classifications
T1190
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=0 <1.26.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

NLnet Labs · Unboundversion=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

T1190Exploit Public-Facing Application

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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