F5 has fixed a critical zero-day bug in its BIG-IP Access Policy Manager (APM) that unknown miscreants are exploiting to remotely execute malicious code. BIG-IP APM is a centralized access management and security proxy that allows users to connect to enterprise networks, applications, APIs, and cloud services via a single login. The flaw, tracked as CVE-2026-94127, is a heap-based buffer overflow that affects BIG-IP APM systems configured as an OAuth Authorization Server, with an access policy and OAuth profile on the same virtual server. It received a critical 9.3 CVSS v4.0 score - so patch now. “We have learned that this vulnerability has been exploited,” F5 said in a Tuesday security advisory. F5 did not immediately respond to our questions, including how many systems have been…