Loofah allowed_uri? does not detect javascript: URIs split by numeric character references without semicolons

Exploitation

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

CVSS 4.0

2.3 · CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary Loofah::HTML5::Scrub.alloweduri? does not correctly reject javascript: or vbscript: URIs when the scheme is split by a numeric character reference that has no trailing semicolon. A browser decodes such references and resolves the URL to an executable javascript: scheme, while alloweduri? reports it safe. This is a bypass of the fix for GHSA-46fp-8f5p-pf2m, which handled numeric character references with a trailing ; (	, 
, 
) but did not cover the forms without semicolons. Details alloweduri? decodes HTML entities with CGI.unescapeHTML, which decodes numeric character references only when they carry a trailing ;. A reference without a semicolon such as &#58 (colon) or &#9 (tab) is left literal, so the scheme-detection check finds no scheme, and the method falls through to its scheme-less path and returns true. A browser, however, decodes numeric character references even without a trailing semicolon. An encoded colon such as &#58 becomes the : scheme separator, so…

Published by the source

21 Jul 2026, 22:03 UTC

Last modified by the source

21 Jul 2026, 22:03 UTC

Source last checked

26 Oct 2026, 15:52 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-5qhf-9phg-95m2

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# Patch Next advisory brief: GHSA-5qhf-9phg-95m2

Advisory: Loofah `allowed_uri?` does not detect `javascript:` URIs split by numeric character references without semicolons
IDs: GHSA-5qhf-9phg-95m2
Record: https://patchnext.com/advisories/ghsa-5qhf-9phg-95m2 (revision 1, source checked 26 Oct 2026, 15:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: loofah 2.25.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems loofah: affected >= 2.25.0, < 2.25.2; fixed in 2.25.2

## Suggested inspection (read-only)
- RubyGems loofah: 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 loofah.
- 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-5qhf-9phg-95m2 (GitHub-reviewed advisory GHSA-5qhf-9phg-95m2 lists affected ranges: RubyGems loofah >=2.25.0 <2.25.2)

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