Critical F5 BIG-IP Bug Under Active Attacks After PoC Exploit Posted Online

CVE-2020-5902 is a critical, unauthenticated remote code execution flaw in the F5 BIG-IP Traffic Management User Interface (TMUI), the appliance's web management console, rooted in a directory/path traversal issue (CWE-22) in undisclosed TMUI pages. It is triggered by sending crafted HTTP(S) requests to the management interface — classically path-traversal URLs beneath the TMUI application on the management port — which lets an attacker bypass authentication, read or delete arbitrary files, and execute commands without credentials. Successful exploitation yields full control of the BIG-IP system, which attackers can use to pivot into networks the appliance fronts, maintain persistence, and deploy ransomware. Any organization running an affected F5 BIG-IP appliance or virtual edition whose TMUI is reachable, or whose management network can be reached, is exposed; F5's installed base spans large enterprises and service providers, so the footprint is broad. Exploitation is confirmed in the wild: the flaw was mass-scanned and exploited within days of its July 2020 disclosure, it is listed in CISA KEV with known ransomware use, and EPSS assigns a ~100% probability of exploitation within 30 days.

Do: Patch immediately using F5's advisory K52145254 — upgrade BIG-IP to a fixed release per the vendor's version matrix, since CISA's required action is applying vendor updates. Until patched, restrict TMUI/management-interface access to trusted source IPs or a VPN (or disable TMUI if unused) and apply F5's published interim workaround. Because ransomware use is confirmed, hunt for indicators of compromise on both patched and unpatched appliances (unexpected files, webshells, modified login pages, new accounts or scheduled tasks) before treating systems as clean.

F5 BIG-IP and BIG-IQ Centralized Management contain a remote code execution vulnerability (CWE-863, improper authorization check) in the iControl REST interface. An unauthenticated attacker with network access to the REST endpoint can send crafted requests to execute arbitrary system commands, create or delete files, and disable services on the appliance or virtual instance. Successful exploitation effectively gives the attacker command-level control of the underlying F5 system, which is sufficient for account creation, persistence, lateral movement, and ransomware staging. Any organization running affected BIG-IP or BIG-IQ releases is exposed, particularly where the management interface or iControl REST is reachable from untrusted networks. Exploitation is confirmed in the wild: the flaw was added to CISA's KEV on 2021-11-03 with known ransomware use, EPSS places the 30-day exploitation probability at 99.9% (top percentile), though no public PoC is cataloged.

Do: Upgrade BIG-IP and BIG-IQ to the fixed releases identified in F5's advisory (K03051234) on an urgent basis, since exploitation is in the wild and ransomware actors use this flaw. Until patched, restrict network access to the management interface and iControl REST to trusted administration networks. Because ransomware use is known, review affected devices for indicators of compromise such as unexpected commands, created or deleted files, and disabled services.