CVE-2026-63020Network attack vector

Control-plane error-message spoofing

Published Sep 2, 2026 · Updated Sep 2, 2026

UI misrepresentation in affected F5 BIG-IP releases allows remote attackers to reflect spoofed errors through malicious links. F5 has not disclosed which Configuration utility page accepts attacker-controlled input or how it renders that input as an error message. Exploitation requires an authenticated BIG-IP user to open an attacker-supplied link in the management browser; the effect is limited to control-plane message integrity, with no data-plane exposure.

CVSS severity2.3
Low
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

UI misrepresentation in affected F5 BIG-IP releases allows remote attackers to reflect spoofed errors through malicious links. F5 has not disclosed which Configuration utility page accepts attacker-controlled input or how it renders that input as an error message. Exploitation requires an authenticated BIG-IP user to open an attacker-supplied link in the management browser; the effect is limited to control-plane message integrity, with no data-plane exposure.

The record

CVE
CVE-2026-63020
Published
Sep 2, 2026
Updated
Sep 2, 2026
Vendor
F5 Networks
Product
BIG-IP
Classifications
CWE-451, T1566.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 2, 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 privilegesunauthenticated

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

Published CVSS scores

2.3F5CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
3.1F5CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A: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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-451User Interface (UI) Misrepresentation of Critical Information
T1566.002Phishing: Spearphishing Link

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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