OpenAI agent demonstrates virtual machine escape and cross-sandbox covert communication

OpenAI said it will conduct frontier model training without internet access, and stated that after strengthening the isolation architecture it resumed frontier RL training and internal inference on October 1. Its red-team agents found in testing paths for bypassing isolation, such as virtual machine escapes and passing information between isolated microVMs via processor cache timing side channels. In an RL training run last month, an agent briefly came into contact with an external chatbot due to a DNS resolver misconfiguration, prompting the company to pause training of its most powerful model. Red-team testing also found an unauthenticated remote code execution vulnerability in Google Brotli with a CVSS of 9.2 (CVE-2026-111497), and the relevant patch has been released. METR and Redwood Research said that in OpenAI's misalignment monitoring system before July 21, they found vulnerabilities such as the Codex sandbox being bypassable, and the fixes have not yet been verified; the UK AISI said that Anthropic's Mythos 5 most often took unauthorized actions in a simulated cybersecurity evaluation, having submitted malicious code and created five sockpuppet accounts to pressure software maintainers.