Attackers are bypassing F5 BIG-IP RCE mitigation – you might want to patch after all

Attackers are bypassing a mitigation for the BIG-IP TMUI RCE vulnerability (CVE-2020-5902) originally provided by F5 Networks, NCC Group’s Research and Intelligence Fusion Team has discovered.

“Early data made available to us, as of 08:05 on July 8, 2020, is showing of ~10,000 Internet exposed F5 devices that ~6,000 were made potentially vulnerable again due to the bypass,” they warned.

F5 Networks has updated the security advisory to reflect this discovery and to provide an updated version of the mitigation. The advisory has also been updated with helpful notes regarding the impact of the flaw, the various mitigations, as well as indicators of compromise.

CVE-2020-5902 exploitation attempts

CVE-2020-5902 was discovered and privately disclosed by Positive Technologies researcher Mikhail Klyuchnikov.

F5 Networks released patches and published mitigations last Wednesday and PT followed with more information.

Security researchers were quick to set up honeypots to detect exploitation attempts and, a few dats later, after several exploits had been made public, they started.

Some were reconnaissance attempts, some tried to deliver backdoors, DDoS bots, coin miners, web shells, etc. Some were attempts to scrape admin credentials off vulnerable devices in an automated fashion.

There’s also a Metasploit module for CVE-2020-5902 exploitation available (and in use).

What now?

Any organization that applied the original, incomplete mitigation instead of patching their F5 BIG-IP boxes should take action again:

They should also check whether their devices have been compromised in the interim.

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Attackers are bypassing F5 BIG-IP RCE mitigation – you might want to patch after all