OpenAI has released GPT-5.6-Cyber, a new model built on GPT-5.6 Sol and trained to find zero-day vulnerabilities and build exploit chains, with fewer refusals on higher-risk, dual-use work. The model is available only through Daybreak Red, the higher tier of OpenAI’s vetted access program for cybersecurity professionals. According to the company, GPT-5.6-Cyber completed 95% of requests involving exploit chains, authentication bypass, and privilege escalation in an internal benchmark, while the standard, guardrail-enabled version of GPT-5.6 completed 1.5%. OpenAI added that on ExploitGym, which evaluates whether agents can turn known vulnerabilities into working exploits that achieve arbitrary code execution in controlled environments, GPT-5.6-Cyber outperforms both GPT-5.6 Sol and GPT-5.5 Cyber. OpenAI’s own researchers used GPT-5.6-Cyber to find two previously undocumented flaws in V8, the JavaScript engine behind Chrome, that could be chained to corrupt memory and escape the browser’s sandbox. Google fixed the issue and assigned it CVE-2026-15903. The company also identified high-severity vulnerabilities affecting a popular mobile operating system, a widely used database, and an operating system kernel, but did not publicly identify the affected projects, saying it is working with partners and the open-source community to disclose and remediate the vulnerabilities.