F5 Networks have addressed critical vulnerabilities in its BIG-IP networking device. The vulnerability tracked as CVE-2021-23031 is a privilege escalation issue on BIG-IP Advanced Web Application Firewall (WAF) and Application Security Manager (ASM) Traffic Management User Interface (TMUI).


According to the security advisory, when this vulnerability is exploited, an authenticated attacker with access to the Configuration utility can execute arbitrary system commands, create or delete files, and/or disable services.

Similarly, this flaw may result in complete system compromise. BIG-IP systems have the option of running in Appliance mode.

This appliance mode is designed to meet the needs of customers in, particularly sensitive sectors by limiting the BIG-IP system administrative access to match that of a typical network appliance and not a multi-user UNIX device.

The flaw has a severity score of 8.8, nevertheless, the security advisory says, for customers using the Appliance Mode, applies some technical restrictions, the severity score raises to 9.9 out of 10.

Also, only a limited number of customers are impacted by the issue in a critical mode.

“The limited number of customers using Appliance mode have Scope: Changed, which raises the CVSSv3 score to 9.9”, reads the security advisory.

ProductBranchVersions known to be vulnerable1Fixes introduced inSeverityCVSSv3 score2Vulnerable component or feature
BIG-IP (Advanced WAF and ASM)16.x16.0.0 –

High — Critical – Appliance mode only3

TMUI/Configuration utility
15.x15.1.0 –
14.x14.1.0 – 14.1.414.1.4.1
13.x13.1.0 – 13.1.313.1.4
12.x12.1.0 – 12.1.512.1.6
11.x11.6.1 – 11.6.511.6.5.3
BIG-IP (all other modules)16.xNoneNot applicableNot vulnerableNoneNone
15.xNoneNot applicable
14.xNoneNot applicable
13.xNoneNot applicable
12.xNoneNot applicable
11.xNoneNot applicable
BIG-IQ Centralized Management8.xNoneNot applicableNot vulnerable4NoneNone
7.xNoneNot applicable
6.xNoneNot applicable
F5OS1.xNoneNot applicableNot vulnerableNoneNone
Traffix SDC5.xNoneNot applicableNot vulnerableNoneNone

 List of Issues Addressed by F5

F5 mentions that users can eliminate this vulnerability by installing a version listed in the Fixes column.

F5 addressed 30 high-severity vulnerabilities in multiple products, which include authenticated remote command execution flaws, cross-site scripting (XSS) issues, request forgery issues, insufficient permission, and denial-of-service flaws.


F5 states that the only mitigation is to remove access for users who are not completely trusted since this attack is conducted by legitimate and authenticated users.

  • Block Configuration utility access through self IP addresses.
  • Block Configuration utility access through the management interface These mitigations restrict access to the Configuration utility to only trusted networks or devices, thereby limiting the attack surface.
Guru is an Ex-Security Engineer at Comodo Cybersecurity. Co-Founder - Cyber Security News & GBHackers On Security.


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