OpenAI Releases Full Version of GPT-5.5-Cyber, Outperforms Mythos 5 on CyberGym Benchmark

Odaily reported that OpenAI announced an upgrade to its Daybreak network defense toolchain, officially launching the full version of the GPT-5.5-Cyber model tailored for cybersecurity defense scenarios.

In the CyberGym benchmark test, which evaluates the ability of AI agents to reproduce known vulnerabilities, GPT-5.5-Cyber achieved a single-model score of 85.6%, surpassing GPT-5.5’s 81.8% and Anthropic Mythos 5’s 83.8%.

OpenAI stated that as AI significantly enhances the efficiency of vulnerability discovery, the core bottleneck in cybersecurity is shifting from "finding vulnerabilities" to "automatically fixing them." To this end, the company has simultaneously upgraded the Codex Security plugin, enabling developers to automatically analyze vulnerabilities and generate fix patches within the Codex environment. Since the preview release in March this year, Codex Security has scanned over 30 million code commits and autonomously confirmed fixes for 500,000 security defects. The new version also supports CodeQL query integration and SARIF standard file export.

Additionally, OpenAI has partnered with organizations such as Trail of Bits and HackerOne to launch the "Patch the Planet" open-source security project. This initiative provides ChatGPT Pro subscriptions and API credits to over 30 major open-source projects, including cURL and Go, with security expert teams manually verifying patch quality. Regarding the Daybreak partner program, security vendors such as Palo Alto Networks and Wiz have already integrated the relevant capabilities.