CVE-2026-40435Network attack vector

Unauthenticated endpoint access via incomplete IP restrictions

Published May 13, 2026 · Updated May 13, 2026

Access-control bypass in F5 BIG-IP allows remote attackers at blocked IP addresses to connect to restricted httpd endpoints. The configured IP-based restriction is not applied to every httpd endpoint; F5 has not identified the omitted endpoints or disclosed the implementation error that skips enforcement. The flaw is reachable without authentication only when IP-based httpd restrictions are configured, and the published impact is limited to unauthorized access to information exposed by those endpoints.

CVSS severity6.9
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Access-control bypass in F5 BIG-IP allows remote attackers at blocked IP addresses to connect to restricted httpd endpoints. The configured IP-based restriction is not applied to every httpd endpoint; F5 has not identified the omitted endpoints or disclosed the implementation error that skips enforcement. The flaw is reachable without authentication only when IP-based httpd restrictions are configured, and the published impact is limited to unauthorized access to information exposed by those endpoints.

The record

CVE
CVE-2026-40435
Published
May 13, 2026
Updated
May 13, 2026
Vendor
F5 Networks
Product
BIG-IP
Classifications
CWE-420, T1190
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=16.1.0 <*
  2. Affected versionversion=17.1.0 <17.1.3.1
  3. Affected versionversion=17.5.0 <17.5.1.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · BIG-IPversion=16.1.0 <*; version=17.1.0 <17.1.3.1; version=17.5.0 <17.5.1.4

Published CVSS scores

5.3F5 NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
6.9F5 NetworksCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/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 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-420Unprotected Alternate Channel
T1190Exploit Public-Facing Application

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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