Enterprise organizations using F5 Networks' BIG-IP and BIG-IQ application delivery technologies are being urged to immediately update their systems to address multiple critical vulnerabilities in the products.

Several of the vulnerabilities enable remote attackers to take complete control of the systems to execute malicious code, disable services, create or delete files, and take other malicious actions.

"Unlike previous notable F5 exploits, not all of these can be easily hand-waved away by restricting external access to the administrative interfaces known as the 'control plane,'" says Justin Rhinehart, senior analyst at Bishop Fox. Two critical exploits disclosed this week affect the so-called data plane, which is the part responsible for handing any and all traffic going through the BIG-IP platform, he says. The only way to mitigate these exploits is by patching.

In a worst-case scenario, Rhinehart says, an attacker can use a vulnerable F5 BIG-IP appliance to break into the broader enterprise network.  

"Remote command execution in a location with such privileged access is absolutely the stuff of nightmares," he says, "Attackers can use these devices to gain a foothold on a victim's network [and] attack sensitive targets that are not usually accessible from the outside world."

F5 Networks on Wednesday disclosed four critical vulnerabilities in BIG-IP 11.6 or 12.x and newer — one of which also impacted versions 6.x and 7.x of the company's BIG-IQ centralized management technology. In addition, F5 announced seven high severity bugs and 10 medium security issues impacting BIG-IP and BIG-IQ — technologies that many enterprise organizations use for a range of application delivery services, such as access control, load balancing, and app security. The company has released patches for all disclosed issues.

In a blog, F5 networks describes the vulnerabilities as impacting all BIG-IP and BIG-IQ customers and instances. The vendor urges customers to update their installations of these technologies to the fixed versions as quickly as possible. It was a sentiment echoed by the Department of Homeland Security's Cybersecurity and Information Security Agency (CISA) in an advisory Wednesday.

"CISA encourages users and administrators review the F5 advisory and install updated software as soon as possible," the agency said.

Last June, CISA warned that F5 Networks' BIG-IP technology presented a big target for attackers because of the access these devices provide to enterprise networks. At that time, the agency was responding to reports about attackers actively exploiting another critical vulnerability in BIG-IP that, like the latest batch of bugs, allowed for complete system compromise.

Critical Impact
The four critical vulnerabilities that F5 Networks announced this week are an unauthenticated remote command execution (RCE) vulnerability in BIG-IP iControl REST interface (CVE-2021-22986); a similar RCE vulnerability in the Traffic Management User Interface (CVE-2021-22987); a buffer-overflow bug in the technology's Traffic Management Microkernel (CVE-2021-22991); and an advanced WAF/ASM buffer-overflow vulnerability (CVE-2021-22992).

All four of the critical flaws have a severity rating of 9 or more, indicating they are considered as highly critical. Two of the bugs allow remote attackers to execute arbitrary system commands and to delete or create files and disable critical service. One of flaws (CVE-2021-22987) gives attackers a way to trigger a total system compromise, and the fourth (CVE-2021-22992) enables attackers to execute denial-of-service attacks.

Rhinehart says vulnerabilities are critical because the BIG-IP platform is meant to control all data entering and exiting a network.

"Unauthenticated remote code execution against any application is scary enough, but their importance, location in the network, and prevalence [of BIG-IP] really takes this one to the next level," he says.

For organizations with the impacted technologies, the RCE flaw in the iControl REST Interface likely poses the biggest immediate threat because of the relative ease with which it can be exploited, Rhinehart says.

"In the weeks and months to come, the two vulnerabilities affecting the data plane [CVE-2021-22991 and CVE-2021-22992] become more and more of a concern as people dig deeper into how they work and write advanced exploits that may allow for remote code executions," he explains.

Companies that cannot immediately update to the latest patched versions F5 announced this week should disable access to the iControl REST interface, though this can be tricky, Rhinehart adds. He recommends organizations that are unsure about how to do this should refer to F5 Networks' guidance on the topic.