A significant security flaw, identified as CVE-2025-20029, has been discovered in F5 Networks’ BIG-IP systems, posing a substantial risk to network infrastructures worldwide. This command injection vulnerability allows authenticated users with low-level privileges to execute arbitrary system commands, potentially leading to full system compromise.
Understanding CVE-2025-20029
CVE-2025-20029 is a command injection vulnerability affecting the Traffic Management Shell (TMSH) command-line interface of F5’s BIG-IP systems. The flaw arises from improper input validation within the TMSH parser, enabling attackers to inject malicious commands that escape the command-line interface’s security restrictions. This vulnerability is present in BIG-IP versions up to 16.1.4.1. Successful exploitation grants attackers root-level access, allowing them to manipulate system configurations, intercept network traffic, and move laterally within connected networks.
Proof-of-Concept Exploit Details
On February 24, 2025, security researchers released a proof-of-concept (PoC) exploit demonstrating the vulnerability’s potential impact. The exploit targets the ‘save sys config’ TMSH command, which operates with root privileges by default. By injecting a payload using shell metacharacters, attackers can split the original command into two parts:
1. A legitimate save operation to the Common configuration partition.
2. An arbitrary command executed via bash.
For example, the payload `save sys config partitions { Common }; bash -c id ; # }` leverages TMSH’s syntax parsing weaknesses. The sequence `};` terminates the save command prematurely, while the subsequent `bash -c id` executes a system call to print the current user’s ID, confirming execution as root.
Exploitation Requirements and Impact
Exploiting this vulnerability requires:
– Access to the TMSH interface via SSH or the iControl REST API.
– Use of binaries whitelisted by F5, such as bash or tcpdump.
– Valid partition names to avoid command failure.
The potential impact of successful exploitation includes:
– Execution of arbitrary system commands with root privileges.
– Creation or deletion of files through the BIG-IP management port.
– Access to self IP addresses.
– Bypassing Appliance mode security restrictions.
Notably, this vulnerability is limited to the control plane, meaning there is no direct exposure to the data plane.
Mitigation and Remediation Steps
F5 has released patches to address this vulnerability in the following versions:
– BIG-IP v17.1.2.2
– BIG-IP v16.1.6
– BIG-IP v15.1.10.7
Organizations are strongly advised to upgrade to these versions immediately.
For systems where immediate patching is not feasible, F5 recommends implementing temporary mitigations:
– Restrict Access to iControl REST:
– Limit access to the iControl REST interface to trusted networks or devices.
– Change the Port Lockdown setting to Allow None for each self IP address. If necessary, use the Allow Custom option, ensuring iControl REST access is disallowed.
– Block iControl REST access through the management interface by restricting management access to trusted users and devices over a secure network.
– Restrict Access to the BIG-IP Command Line via SSH:
– Block SSH access through self IP addresses by changing the Port Lockdown setting to Allow None for each self IP address.
Additionally, organizations should:
– Implement Network Segmentation: Restrict access to management interfaces to trusted sources.
– Monitor Logs: Continuously audit logs for unauthorized save commands or suspicious activity.
– Enable Multi-Factor Authentication (MFA): Reduce risks associated with credential theft and unauthorized access.
Conclusion
CVE-2025-20029 presents a significant risk to network infrastructure, as successful exploitation grants full administrative control over affected BIG-IP devices. The availability of proof-of-concept exploits further increases the urgency for immediate remediation. Organizations using F5 BIG-IP for load balancing, firewall, or application delivery services should treat CVE-2025-20029 as a critical priority. Delayed remediation leaves systems vulnerable to compromise and potential data breaches. Security teams should act swiftly to implement updates and protective measures.
