CyberSecBulletin
CVE-2026-42406NVD status: Analyzed

BIG-IP: Privilege Defined With Unsafe Actions

Published Updated By the CyberSecBulletin desk

CVE-2026-42406 is a high-severity privilege defined with unsafe actions vulnerability in BIG-IP from F5, with a CVSS 3.1 base score of 8.7 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, without any action from a user. The record lists versions 21.0.0.2, 17.5.1.6, 17.1.3.2 as the first without the flaw, so updating BIG-IP to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.15% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update BIG-IP to 21.0.0.2 or 17.5.1.6 or 17.1.3.2, whichever matches your release line, or a later version.
  2. Read the advisory on my.f5.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
F5BIG-IP21.0.0 up to, but not including, 21.0.0.2; 17.5.0 up to, but not including, 17.5.1.6; 17.1.0 up to, but not including, 17.1.3.2; 16.1.0 and later21.0.0.2, 17.5.1.6, 17.1.3.2
F5BIG-IQ8.4.0 and laterNot stated
F5Big-ip Access Policy Manager17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Advanced Firewall Manager17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Advanced Web Application Firewall17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Analytics17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Application Acceleration Manager17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Application Security Manager17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Application Visibility And Reporting17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Automation Toolchain17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Carrier-grade Nat17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Container Ingress Services17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Ddos Hybrid Defender17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Domain Name System17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Edge Gateway17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Fraud Protection Service17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Global Traffic Manager17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Link Controller17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Local Traffic Manager17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Policy Enforcement Manager17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip SSL Orchestrator17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Webaccelerator17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-ip Websafe17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 16.1.0 through 16.1.6; 21.0.0Not stated
F5Big-iq Centralized Management8.4.0 through 8.4.1Not stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
HighAdministrator-level access is required first.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
NoneAvailability is not affected.

Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N. Scored by CNA (f5.com).

Scoring systemScoreSeverityScored by
CVSS 4.08.5HighCNA (f5.com)
CVSS 3.18.7HighCNA (f5.com)

Official description

A vulnerability exists in BIG-IP and BIG-IQ systems where a highly privileged, authenticated attacker with at least the Certificate Manager role can modify configuration objects that allow running arbitrary commands. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Privilege Defined With Unsafe Actions

A particular privilege, role, capability, or right can be used to perform unsafe actions that were not intended, even when it is assigned to the correct entity.

How developers prevent this class of flaw

  • Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
  • Run your code using the lowest privileges that are required to accomplish the necessary tasks. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.

More Privilege Defined With Unsafe Actions vulnerabilities (CWE-267)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in BIG-IP

All BIG-IP vulnerabilities

Recent Privilege Defined With Unsafe Actions vulnerabilities

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