Anthropic’s New Claude Mythos Is So Good at Finding and Exploiting Vulnerabilities That They’re Not Releasing It to the Public

Anthropic’s Frontier Red Team:

Earlier today we announced Claude Mythos Preview, a new general-purpose language model. This model performs strongly across the board, but it is strikingly capable at computer security tasks. In response, we have launched Project Glasswing, an effort to use Mythos Preview to help secure the world’s most critical software, and to prepare the industry for the practices we all will need to adopt to keep ahead of cyberattackers.

This blog post provides technical details for researchers and practitioners who want to understand exactly how we have been testing this model, and what we have found over the past month. We hope this will show why we view this as a watershed moment for security, and why we have chosen to begin a coordinated effort to reinforce the world’s cyber defenses.

“Our new model is so good, it’s too dangerous to release to the public” is a message that sounds like it could be marketing hype. But it seems like it’s probably true. Examples cited by Anthropic include finding and exploiting a 27-year-old OpenBSD bug (that can crash any device running OpenBSD) and an 16-year-old bug in the widely used FFmpeg media processing library.

See also: Techmeme’s extensive roundup.

★ Wednesday, 8 April 2026