CVE-2023-40534Network attack vector

TMM termination via undisclosed HTTP/2 requests

Published Oct 10, 2023 · Updated Sep 19, 2024

Denial of service in affected F5 BIG-IP and BIG-IP Next SPK releases allows remote attackers to terminate TMM through HTTP/2 requests. The TMM HTTP/2 request-processing path fails to release memory after its effective lifetime, but F5 has not disclosed the request form or exact code locus. Exposure requires a virtual server with client-side HTTP/2, HTTP MRF Router, and either an HTTP_REQUEST iRule or Local Traffic Policy; successful exploitation interrupts traffic processing.

CVSS severity7.5
High
EPSS probability0.54%
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 and BIG-IP Next SPK releases allows remote attackers to terminate TMM through HTTP/2 requests. The TMM HTTP/2 request-processing path fails to release memory after its effective lifetime, but F5 has not disclosed the request form or exact code locus. Exposure requires a virtual server with client-side HTTP/2, HTTP MRF Router, and either an HTTP_REQUEST iRule or Local Traffic Policy; successful exploitation interrupts traffic processing.

The record

CVE
CVE-2023-40534
Published
Oct 10, 2023
Updated
Sep 19, 2024
Vendor
F5 Networks
Product
BIG-IP
Classifications
CWE-401, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 10, 2023CVE publishedPublication date reported by the CVE source.
  2. Sep 19, 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=16.1.0 <16.1.4.1.0.13.5-ENG
  2. Affected versionversion=17.1.0 <17.1.0.3.0.23.4-ENG

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · BIG-IPversion=16.1.0 <16.1.4.1.0.13.5-ENG; version=17.1.0 <17.1.0.3.0.23.4-ENG
F5 Networks · BIG-IP Next SPKversion=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 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-401Missing Release of Memory after Effective Lifetime
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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