CVE-2023-23555Network attack vector

Service interruption via undisclosed FastL4 traffic

Published Feb 1, 2023 · Updated Mar 26, 2025

Denial of service in affected F5 BIG-IP VE and SPK releases allows remote attackers to terminate TMM via a FastL4 virtual server. TMM terminates while processing undisclosed traffic, but F5 has not published the packet characteristics or faulty initialization operation. The target must expose a virtual server configured with FastL4; exploitation interrupts traffic processing without reported confidentiality or integrity impact.

CVSS severity7.5
High
EPSS probability0.63%
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 affected F5 BIG-IP VE and SPK releases allows remote attackers to terminate TMM via a FastL4 virtual server. TMM terminates while processing undisclosed traffic, but F5 has not published the packet characteristics or faulty initialization operation. The target must expose a virtual server configured with FastL4; exploitation interrupts traffic processing without reported confidentiality or integrity impact.

The record

CVE
CVE-2023-23555
Published
Feb 1, 2023
Updated
Mar 26, 2025
Vendor
F5 Networks
Product
BIG-IP
Classifications
CWE-665, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 1, 2023CVE publishedPublication date reported by the CVE source.
  2. Mar 26, 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=14.1.5 <14.1.5.3
  2. Affected versionversion=15.1.4 <15.1.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · BIG-IPversion=14.1.5 <14.1.5.3; version=15.1.4 <15.1.8
F5 Networks · BIG-IP Next Service Proxy for Kubernetesversion=1.5.0 <1.6.0

Published CVSS scores

7.5F5 NetworksCVSS: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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-665Improper Initialization
T1499Endpoint Denial of Service

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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