CVE-2021-22977Network attack vector

TMM restart via coordinated HTTP traffic

Published Feb 12, 2021 · Updated Aug 3, 2024

Denial of service in F5 Networks BIG-IP 16.0.0 through 16.0.1 and 14.1.2.4 through 14.1.3 allows remote attackers to restart TMM. F5 has not published the specific TMM parsing or state-handling error triggered by the coordinated malicious client and server exchange. Exploitation requires control of both ends of proxied HTTP traffic and interrupts application traffic while TMM restarts; no data disclosure or modification is reported.

CVSS severity7.5
High
EPSS probability1.06%
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 16.0.0 through 16.0.1 and 14.1.2.4 through 14.1.3 allows remote attackers to restart TMM. F5 has not published the specific TMM parsing or state-handling error triggered by the coordinated malicious client and server exchange. Exploitation requires control of both ends of proxied HTTP traffic and interrupts application traffic while TMM restarts; no data disclosure or modification is reported.

The record

CVE
CVE-2021-22977
Published
Feb 12, 2021
Updated
Aug 3, 2024
Vendor
F5 Networks
Product
BIG-IP
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 12, 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

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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=16.0.0-16.0.1, 14.1.2.4-14.1.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · BIG-IPversion=16.0.0-16.0.1, 14.1.2.4-14.1.3

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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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