Anthropic Publishes a Cross-Industry Jailbreak Severity Scale After a 19-Day Export-Control Suspension

Anthropic has redeployed its Fable 5 model and, alongside it, proposed an industry-wide scale for scoring the severity of AI jailbreaks, developed with Amazon, Microsoft, Google and other partners in its Glasswing group. The framework, the Cyber Jailbreak Severity scale, rates a jailbreak from CJS-0 (informational) to CJS-4 (critical).

The design is based directly on established security practice. Per Let's Data Science, the scale scores four axes, capability gain, breadth of that gain, ease of weaponization, and discoverability, and its bands are exponential rather than linear, so each step represents several times more real-world risk than the one below. It is explicitly modeled on the Common Vulnerability Scoring System (CVSS) that traditional software security has used for years.

The context is what makes this more than a classification system. The framework followed a US Commerce Department export-control order that pulled Fable 5 and Mythos 5 offline worldwide for 19 days, from June 12 to July 1, after Amazon researchers found a jailbreak. Five labs are targeting August 1 to adopt the scale. A shared scoring vocabulary lets regulators tie an enforcement trigger to a defined severity band rather than to any single reported exploit, which both benefits and constrains the labs that wrote it.