CVE-2023-4236Network attack vector

Remote service crash via DNS-over-TLS structure reuse

Published Sep 20, 2023 · Updated Feb 13, 2025

Reachable assertion in Internet Systems Consortium BIND 9 9.18.0 through 9.18.18 allows remote attackers to crash named via DNS-over-TLS queries. The DNS-over-TLS networking path incorrectly reuses internal data structures under significant query load, triggering an assertion failure that terminates named. The condition also affects Supported Preview Edition 9.18.11-S1 through 9.18.18-S1, requires a configured DNS-over-TLS listener, and interrupts DNS service by crashing named; DNS-over-HTTPS is unaffected.

CVSS severity7.5
High
EPSS probability2.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reachable assertion in Internet Systems Consortium BIND 9 9.18.0 through 9.18.18 allows remote attackers to crash named via DNS-over-TLS queries. The DNS-over-TLS networking path incorrectly reuses internal data structures under significant query load, triggering an assertion failure that terminates named. The condition also affects Supported Preview Edition 9.18.11-S1 through 9.18.18-S1, requires a configured DNS-over-TLS listener, and interrupts DNS service by crashing named; DNS-over-HTTPS is unaffected.

The record

CVE
CVE-2023-4236
Published
Sep 20, 2023
Updated
Feb 13, 2025
Vendor
Internet Systems Consortium
Product
BIND 9
Classifications
CWE-617, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 20, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 13, 2025Record 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=9.18.0 <=9.18.18
  2. Affected versionversion=9.18.11-S1 <=9.18.18-S1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Internet Systems Consortium · BIND 9version=9.18.0 <=9.18.18; version=9.18.11-S1 <=9.18.18-S1

Published CVSS scores

7.5Internet Systems ConsortiumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-617Reachable Assertion
T1499.004Application 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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