CVE-2026-41523: vLLM: Security Check Bypass via assert Statement in Activation Function Loading Allows Arbitrary Code Execution

An assert-based security check in vLLM’s activation function loading allows any unauthenticated attacker to achieve arbitrary code execution on the server by publishing a malicious HuggingFace model, when vLLM runs in Python optimized mode (python -O or PYTHONOPTIMIZE=1).