CVE-2026-25500: Rack

Medium severity, CVSS 5.4. EPSS: 0.3% chance of exploitation in the next 30 days.

Rack is a modular Ruby web server interface. Prior to versions 2.2.22, 3.1.20, and 3.2.5, `Rack::Directory` generates an HTML directory index where each file entry is rendered as a clickable link. If a file exists on disk whose basename starts with the `javascript:` scheme (e.g. `javascript:alert(1)`), the generated index contains an anchor whose `href` is exactly `javascript:alert(1)`. Clicking the entry executes JavaScript in the browser (demonstrated with `alert(1)`). Versions 2.2.22, 3.1.20, and 3.2.5 fix the issue.

Affected products

• Rack Rack: before 2.2.22 (fixed in 2.2.22); from 3.0.0, before 3.1.20 (fixed in 3.1.20); from 3.2.0, before 3.2.5 (fixed in 3.2.5)

Published 2026-02-18. Last modified 2026-06-17.