CVE-2026-39459: RCE in F5 BIG-IP via iControl REST
Platform
linux
Component
bigip
Fixed in
21.0.0.2
CVE-2026-39459 is a Remote Code Execution (RCE) vulnerability affecting F5 BIG-IP versions 16.1.0 through 21.0.0.2. A highly privileged, authenticated attacker with the Manager role can leverage this flaw to create configuration objects that allow the execution of arbitrary commands on the system. This vulnerability is rated HIGH severity (CVSS 7.2) and requires immediate attention to prevent potential compromise.
Impact and Attack Scenarios
Successful exploitation of CVE-2026-39459 allows an attacker to gain complete control over the affected BIG-IP system. This includes the ability to execute arbitrary commands with the privileges of the Manager role, potentially leading to data exfiltration, system modification, and denial of service. The attacker could install malware, pivot to other systems on the network, or disrupt critical services. The blast radius extends to any system accessible from the compromised BIG-IP, making it a significant security risk. This vulnerability shares similarities with other iControl REST vulnerabilities, highlighting the importance of secure configuration and access controls.
Exploitation Context
CVE-2026-39459 was published on May 13, 2026. Its severity is pending evaluation for inclusion on the CISA Known Exploited Vulnerabilities (KEV) catalog. Public proof-of-concept (POC) code is currently unavailable, but the vulnerability's nature suggests a high likelihood of exploitation once available. Monitor security advisories and threat intelligence feeds for any indications of active exploitation campaigns.
Threat Intelligence
Exploit Status
CISA SSVC
CVSS Vector
What do these metrics mean?
- Attack Vector
- Network — remotely exploitable over the internet. No physical or local access required. Widest attack surface.
- Attack Complexity
- Low — no special conditions required. Attacker can exploit reliably without depending on rare configurations or timing.
- Privileges Required
- High — admin or privileged account required to exploit.
- User Interaction
- None — attack is automatic and silent. Victim does nothing: no click, no file open.
- Scope
- Unchanged — impact is limited to the vulnerable component itself.
- Confidentiality
- High — complete confidentiality loss. Attacker can read all data: credentials, keys, personal data.
- Integrity
- High — attacker can write, modify, or delete any data: databases, config files, or code.
- Availability
- High — complete crash or resource exhaustion. Full denial of service.
Affected Software
Weakness Classification (CWE)
Timeline
- Reserved
- Published
- Modified
Mitigation and Workarounds
The primary mitigation for CVE-2026-39459 is to upgrade to F5 BIG-IP version 21.0.0.2 or later, which contains the fix. If immediate upgrade is not possible, consider implementing temporary workarounds such as restricting access to the iControl REST interface to trusted sources only. Implement strict authentication and authorization policies, ensuring that only authorized users with the minimum necessary privileges can access the system. Review and audit existing iControl REST configurations to identify and remove any potentially malicious objects. After upgrading, verify the fix by attempting to create a configuration object that executes a command and confirming that the attempt is denied.
How to fix
Actualice a una versión corregida de F5 BIG-IP. Las versiones corregidas son 21.0.0.2, 17.5.1.6 y 17.1.3.2. Consulte la nota de seguridad de F5 para obtener más detalles y pasos de mitigación.
Frequently asked questions
What is CVE-2026-39459 — RCE in F5 BIG-IP?
CVE-2026-39459 is a Remote Code Execution vulnerability in F5 BIG-IP versions 16.1.0–21.0.0.2. An authenticated attacker can execute arbitrary commands, potentially gaining full control of the system.
Am I affected by CVE-2026-39459 in F5 BIG-IP?
You are affected if you are running F5 BIG-IP versions 16.1.0 through 21.0.0.2 and have not upgraded to a patched version. Check your BIG-IP version immediately.
How do I fix CVE-2026-39459 in F5 BIG-IP?
Upgrade to F5 BIG-IP version 21.0.0.2 or later. As a temporary workaround, restrict access to the iControl REST interface and enforce strict authentication policies.
Is CVE-2026-39459 being actively exploited?
While no public exploits are currently available, the vulnerability's nature suggests a high likelihood of exploitation. Monitor security advisories and threat intelligence feeds.
Where can I find the official F5 advisory for CVE-2026-39459?
Refer to the official F5 Security Advisory for CVE-2026-39459 on the F5 website: [https://www.f5.com/security/center/advisory/f5-security-advisory-39459](https://www.f5.com/security/center/advisory/f5-security-advisory-39459)
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