New serious vulnerabilities spiked around release of Claude Mythos Preview
In April 2026, Anthropic announced that its Claude Mythos Preview model could autonomously discover and exploit cybersecurity vulnerabilities. Subsequently, Anthropic and OpenAI launched efforts to use frontier models to harden critical software. Data shows that high- and critical-severity CVEs increased by more than 3.5x in June compared to the previous monthly record.
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In April 2026, Anthropic announced that its latest internal model (Claude Mythos Preview) was capable of autonomous cybersecurity vulnerability discovery and exploitation. Since then, both Anthropic and OpenAI have launched efforts to use frontier models to harden critical software before malicious actors are able to use the same models for harm.
We show that the number of Common Vulnerabilities and Exposures (CVEs) jumped significantly following these announcements. Compared to the previous monthly record before the Mythos Preview announcement, the number of high- and critical-severity vulnerabilities increased more than 3.5x in June.