---
title: "Claude Mythos Preview \ red.anthropic.com"
source: "https://red.anthropic.com/2026/mythos-preview/"
domain: "red.anthropic.com"
type: "article"
summarized_at: "2026-04-10"
canonical: "https://tl-dr.cc/s/claude-mythos-preview-red-anthropic-com-1tpH"
---

# Claude Mythos Preview \ red.anthropic.com

**Source:** [red.anthropic.com](https://red.anthropic.com/2026/mythos-preview/)  
**Summarized:** 2026-04-10  

- Claude Mythos Preview demonstrates unprecedented capability to autonomously discover and exploit zero-day vulnerabilities across operating systems, web browsers, and critical software—finding subtle bugs ranging from 27 years old to previously undetected in heavily audited codebases like FFmpeg and memory-safe VMMs.
- These exploit capabilities emerged unexpectedly as byproducts of general improvements in code reasoning and autonomy rather than explicit training, enabling non-expert users to develop working exploits overnight and achieving dramatic improvements over prior models (181 working exploits vs. 2 for Opus 4.6 on Firefox vulnerabilities).
- Mythos Preview identified thousands of high- and critical-severity vulnerabilities through a responsible disclosure process using agentic scaffolds that autonomously hypothesize, test, and validate bugs; human validators confirmed 89% of severity assessments matched expert review exactly.
- The model successfully reverse-engineered complex exploits including JIT heap sprays escaping sandboxes, KASLR bypasses, ROP chain construction, and guest-to-host memory corruption in virtual machines, demonstrating qualitative advances beyond fuzzing and human-led security review.
- Anthropic launched Project Glasswing to distribute Mythos Preview to critical industry partners and open-source developers first, aiming to shift the defensive advantage toward security practitioners before broader availability creates a transitional period where attackers might gain asymmetric advantage.

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*AI summary by [tl;dr](https://tl-dr.cc) · [View full page](https://tl-dr.cc/s/claude-mythos-preview-red-anthropic-com-1tpH)*