XSS in Rack
CVE-2026-25500
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.
Vulnerability class: XSS (Cross-Site Scripting)
EPSS: 0.002 (13.2th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.
Affected products
- Rack — versions < 2.2.22, >= 3.0.0.beta1, < 3.1.20, >= 3.2.0, < 3.2.5
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Mitigation, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-25500?
- CVE-2026-25500 is a medium-severity vulnerability in Rack, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-02-18.
- How severe is CVE-2026-25500?
- Medium severity. CVSS v3 base score is 5.4 out of 10.