Stored XSS in Rack::Directory via javascript: filenames rendered into anchor href

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.4 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2026-25500: 0.27% estimated exploitation activity in the next 30 days; percentile 19.15 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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 begins with the javascript: scheme (e.g. javascript:alert(1)), the generated index includes an anchor whose href attribute is exactly javascript:alert(1). Clicking this entry executes arbitrary JavaScript in the context of the hosting application. This results in a client-side XSS condition in directory listings generated by Rack::Directory. Details Rack::Directory renders directory entries using an HTML row template similar to: The %s placeholder is populated directly with the file’s basename. If the basename begins with javascript:, the resulting HTML contains an executable JavaScript URL: Because the value is inserted directly into the href attribute without scheme validation or normalization, browsers interpret it as a JavaScript URI. When a user clicks the link, the JavaScript executes in the origin of the Rack application.…

Published by the source

17 Feb 2026, 18:46 UTC

Last modified by the source

10 Mar 2026, 18:41 UTC

Source last checked

26 Oct 2026, 15:51 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-whrj-4476-wvmp

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# Patch Next advisory brief: CVE-2026-25500

Advisory: Stored XSS in Rack::Directory via javascript: filenames rendered into anchor href
IDs: CVE-2026-25500, GHSA-whrj-4476-wvmp
Record: https://patchnext.com/advisories/cve-2026-25500 (revision 1, source checked 26 Oct 2026, 15:51 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: rack 3.2.5, 3.1.20, 2.2.22. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems rack: affected < 2.2.22; >= 3.0.0.beta1, < 3.1.20; >= 3.2.0, < 3.2.5; fixed in 3.1.20, 3.2.5, 2.2.22

## Suggested inspection (read-only)
- RubyGems rack: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on rack.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-whrj-4476-wvmp (GitHub-reviewed advisory GHSA-whrj-4476-wvmp lists affected ranges: RubyGems rack >=0 =3.0.0.beta1 =3.2.0 <3.2.5)

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