CVE-2026-42406 - F5 BIG-IP and BIG-IQ Authenticated Remote Code Execution

CVE-2026-42406 is a vulnerability affecting F5 BIG-IP and BIG-IQ systems. A threat actor with high privileges and valid authentication credentials, specifically requiring at least the Certificate Manager role, can exploit this flaw. By modifying configuration objects within the system, the attacker can inject and execute arbitrary commands. This vulnerability poses a significant risk to organizations using these F5 products, as successful exploitation can lead to complete system compromise and unauthorized access to sensitive data. Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Attack Chain

1. The attacker gains initial access to the BIG-IP or BIG-IQ system through valid credentials with at least Certificate Manager privileges.
2. The attacker authenticates to the administrative interface of the BIG-IP or BIG-IQ system.
3. The attacker identifies modifiable configuration objects within the system.
4. The attacker modifies a configuration object to inject malicious commands.
5. The system processes the modified configuration object.
6. The injected commands are executed within the system context.
7. The attacker achieves arbitrary command execution on the system.
8. The attacker leverages the executed commands to escalate privileges, move laterally within the network, or exfiltrate sensitive data.

Impact

Successful exploitation of CVE-2026-42406 can lead to complete compromise of the BIG-IP or BIG-IQ system. This can result in unauthorized access to sensitive data, disruption of services, and the potential for further lateral movement within the network. Given the critical role that BIG-IP and BIG-IQ systems play in network infrastructure, a successful attack can have significant consequences for affected organizations.

Recommendation

• Apply the mitigations recommended in F5’s security advisory [https://my.f5.com/manage/s/article/K000160971].
• Monitor authentication logs for suspicious login activity to the BIG-IP or BIG-IQ administrative interface.
• Deploy the Sigma rule detecting configuration changes by highly privileged accounts to your SIEM and tune for your environment.
• Review user roles and permissions to ensure the principle of least privilege is enforced.