CVE-2021-23032Network attack vector

TMM termination via undisclosed DNS responses

Published Sep 14, 2021 · Updated Aug 3, 2024

Denial of service in affected F5 BIG-IP DNS releases allows remote attackers to interrupt DNS service via undisclosed DNS responses. TMM processes the responses under non-default Wide IP and pool settings, but F5 has not disclosed the invalid input or erroneous processing operation that terminates it. The non-default settings are required; successful triggering terminates TMM and interrupts traffic processing without reported data disclosure or modification.

CVSS severity7.5
High
EPSS probability0.93%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Denial of service in affected F5 BIG-IP DNS releases allows remote attackers to interrupt DNS service via undisclosed DNS responses. TMM processes the responses under non-default Wide IP and pool settings, but F5 has not disclosed the invalid input or erroneous processing operation that terminates it. The non-default settings are required; successful triggering terminates TMM and interrupts traffic processing without reported data disclosure or modification.

The record

CVE
CVE-2021-23032
Published
Sep 14, 2021
Updated
Aug 3, 2024
Vendor
F5 Networks
Product
BIG-IP DNS
Classifications
CWE-20, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 14, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=16.x before 16.1.0, 15.1.x before 15.1.3.1, 14.1.x before 14.1.4.4, and all versions of 13.1.x and 12.1.x

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · BIG-IP DNSversion=16.x before 16.1.0, 15.1.x before 15.1.3.1, 14.1.x before 14.1.4.4, and all versions of 13.1.x and 12.1.x

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS: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-20Improper Input Validation
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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo