VERY IMPORTANT

A China-linked threat cluster, UNC5221, is actively targeting organizations using F5 BIG-IP following a confirmed breach of F5's internal development data. The stolen data includes portions of BIG-IP source code and vulnerability information, raising the risk of rapid 0-day discovery and weaponization. CISA issued an Emergency Directive warning of an imminent threat to federal networks. The attackers deployed a Go-based ELF backdoor called BRICKSTORM, which establishes a persistent C2 tunnel using WebSocket and employs various techniques to evade detection. The backdoor can turn a BIG-IP device into a stealth egress point and internal proxy. F5 has disclosed over twenty vulnerabilities affecting various products, urging immediate patching and security measures.