CVE-2025-53521

Pierluigi Paganini September 09, 2026
PoisonedRefresh: A Fileless Linux Rootkit That Injects PHP Web Shells Into F5 BIG-IP APM Server Memory

PoisonedRefresh rootkit injects PHP web shells into F5 BIG-IP APM Apache memory, leaving no disk artifacts. SophosLabs published a detailed technical analysis on September 8, 2026, of a Linux implant, dubbed PoisonedRefresh by ESET, they found in compromised F5 BIG-IP Access Policy Manager environments. Sophos tracks it as Linux/Agnt-IC. F5 has confirmed exploitation of the […]

Pierluigi Paganini April 06, 2026
Attackers Exploit RCE Flaw as 14,000 F5 BIG-IP APM Instances Remain Exposed

Over 14,000 F5 BIG-IP APM instances remain exposed online, as attackers actively exploit a critical remote code execution flaw CVE-2025-53521. Over 14,000 F5 BIG-IP APM instances remain exposed online, with attackers actively exploiting the critical remote code execution vulnerability CVE-2025-53521 (CVSS ver. 3.1 score of 9.8), the nonprofit security organization Shadowserver warns. The vulnerability in BIG-IP […]