CVE-2021-23003Network attack vector

Remote service interruption via MPTCP TMM crash

Published Mar 31, 2021 · Updated Aug 3, 2024

Denial of service in F5 BIG-IP allows remote attackers to crash the TMM process via crafted MPTCP traffic through a standard virtual server. The Traffic Management Microkernel mishandles an undisclosed MPTCP traffic pattern and writes a core file instead of continuing packet processing. The standard virtual server must be reachable; no authentication or user interaction is required, and the TMM crash interrupts traffic.

CVSS severity7.5
High
EPSS probability0.96%
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 BIG-IP allows remote attackers to crash the TMM process via crafted MPTCP traffic through a standard virtual server. The Traffic Management Microkernel mishandles an undisclosed MPTCP traffic pattern and writes a core file instead of continuing packet processing. The standard virtual server must be reachable; no authentication or user interaction is required, and the TMM crash interrupts traffic.

The record

CVE
CVE-2021-23003
Published
Mar 31, 2021
Updated
Aug 3, 2024
Vendor
F5 Networks
Product
BIG-IP
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 31, 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 16.0.1.1, 15.1.x before 15.1.2, 14.1.x before 14.1.3.1, 13.1.x before 13.1.3.6, 12.1.x before 12.1.5.3, 11.6.x before 11.6.5.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · BIG-IPversion=16.0.x before 16.0.1.1, 15.1.x before 15.1.2, 14.1.x before 14.1.3.1, 13.1.x before 13.1.3.6, 12.1.x before 12.1.5.3, 11.6.x before 11.6.5.3

Published CVSS scores

5.0NISTAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NISTCVSS: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

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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