CVE-2021-23039Network attack vector

Service interruption via undisclosed IPsec requests

Published Sep 14, 2021 · Updated Aug 3, 2024

Denial of service in F5 Networks BIG-IP allows remote authenticated users to terminate TMM through undisclosed IPsec requests. F5 has not disclosed how the Traffic Management Microkernel mishandles the requests beyond mapping the flaw to improper input validation. Reachability requires IPsec configuration and an already-negotiated Security Association; successful exploitation interrupts traffic processing.

CVSS severity7.5
High
EPSS probability0.95%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in F5 Networks BIG-IP allows remote authenticated users to terminate TMM through undisclosed IPsec requests. F5 has not disclosed how the Traffic Management Microkernel mishandles the requests beyond mapping the flaw to improper input validation. Reachability requires IPsec configuration and an already-negotiated Security Association; successful exploitation interrupts traffic processing.

The record

CVE
CVE-2021-23039
Published
Sep 14, 2021
Updated
Aug 3, 2024
Vendor
F5 Networks
Product
BIG-IP
Classifications
CWE-20, T1499.004
Attack vector
network
Privileges
authenticated

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=16.0.x before 16.0.1.2, 15.1.x before 15.1.3, 14.1.x before 14.1.2.8, and all versions of 13.1.x and 12.1.x

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

F5 Networks · BIG-IPversion=16.0.x before 16.0.1.2, 15.1.x before 15.1.3, 14.1.x before 14.1.2.8, and all versions of 13.1.x and 12.1.x

Published CVSS scores

7.1NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:C
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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
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

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Your stack

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