CVE-2026-66842Network attack vector

Authenticated privilege escalation via undisclosed TMUI request

Published Sep 2, 2026 · Updated Sep 3, 2026

Privilege escalation in F5 BIG-IP and BIG-IQ allows remote authenticated users to create administrative accounts through TMUI. F5 identifies server-side request forgery in TMUI but has not published the request path or server-side validation failure. Any authenticated role with network access to the management interface can gain administrative control of the control plane; the data plane is not exposed.

CVSS severity8.8
High
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Privilege escalation in F5 BIG-IP and BIG-IQ allows remote authenticated users to create administrative accounts through TMUI. F5 identifies server-side request forgery in TMUI but has not published the request path or server-side validation failure. Any authenticated role with network access to the management interface can gain administrative control of the control plane; the data plane is not exposed.

The record

CVE
CVE-2026-66842
Published
Sep 2, 2026
Updated
Sep 3, 2026
Vendor
F5 Networks
Product
BIG-IP
Classifications
CWE-918, T1136.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 3, 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=17.1.0 <17.1.3.4
  2. Affected versionversion=17.5.0 <17.5.1.8
  3. Affected versionversion=21.0.0 <21.0.0.3
  4. Affected versionversion=21.1.0 <21.1.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

F5 Networks · BIG-IPversion=17.1.0 <17.1.3.4; version=17.5.0 <17.5.1.8; version=21.0.0 <21.0.0.3; version=21.1.0 <21.1.0.1
F5 Networks · BIG-IQversion=8.4.0 <8.4.2.1

Published CVSS scores

8.8F5CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
8.7F5CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-918Server-Side Request Forgery (SSRF)
T1136.001Create Account: Local Account

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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