CVE-2026-40618Network attack vector

Unauthenticated TMM termination via undisclosed SSL traffic

Published May 13, 2026 · Updated May 13, 2026

Incorrect buffer-size calculation in F5 BIG-IP products allows remote attackers to terminate TMM with undisclosed SSL/TLS traffic. F5 identifies the Traffic Management Microkernel as the failing component but has not disclosed the calculation or traffic pattern that triggers it. Reachability requires an SSL-enabled virtual server on VE without QAT or hardware with crypto.hwacceleration disabled; successful exploitation interrupts traffic processing.

CVSS severity8.7
High
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect buffer-size calculation in F5 BIG-IP products allows remote attackers to terminate TMM with undisclosed SSL/TLS traffic. F5 identifies the Traffic Management Microkernel as the failing component but has not disclosed the calculation or traffic pattern that triggers it. Reachability requires an SSL-enabled virtual server on VE without QAT or hardware with crypto.hwacceleration disabled; successful exploitation interrupts traffic processing.

The record

CVE
CVE-2026-40618
Published
May 13, 2026
Updated
May 13, 2026
Vendor
F5 Networks
Product
BIG-IP Next for Kubernetes
Classifications
CWE-131, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2026CVE publishedPublication date reported by the CVE source.
  2. May 13, 2026Record 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=2.0.0 <2.2.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · BIG-IP Next for Kubernetesversion=2.0.0 <2.2.0
F5 Networks · BIG-IPversion=16.1.0 <*; version=17.1.0 <17.1.3.1; version=17.5.0 <17.1.5.4; version=21.0.0 <21.0.0.1
F5 Networks · BIG-IP Next CNFversion=1.1.0 <*; version=2.0.0 <*
F5 Networks · BIG-IP Next Service Proxy for Kubernetesversion=1.7.0 <*; version=2.0.0 <*

Published CVSS scores

7.5F5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7F5CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L

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-131Incorrect Calculation of Buffer Size
T1499.004Application or System Exploitation 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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