Loofah has improper detection of disallowed URIs via allowed_uri?

Exploitation

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

CVSS 4.0

2.3 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/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: URIs when the scheme is split by HTML entity-encoded control characters such as 
 (carriage return), 
 (line feed), or 	 (tab). Details The alloweduri? method strips literal control characters before decoding HTML entities. Payloads like java
script:alert(1) survive the control character strip, then 
 is decoded to a carriage return, producing java\rscript:alert(1). Note that the Loofah sanitizer's default sanitize() path is not affected because Nokogiri decodes HTML entities during parsing before Loofah evaluates the URI protocol. This issue only affects direct callers of the alloweduri? string-level helper when passing HTML-encoded strings. Impact Applications that call Loofah::HTML5::Scrub.alloweduri? to validate user-controlled URLs and then render approved URLs into href or other browser-interpreted URI attributes may be vulnerable to cross-site scripting (XSS). This only affects…

Published by the source

26 Mar 2026, 22:19 UTC

Last modified by the source

26 Mar 2026, 22:19 UTC

Source last checked

26 Oct 2026, 15:51 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-2j22-pr5w-6gq8

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# Patch Next advisory brief: GHSA-2j22-pr5w-6gq8

Advisory: Loofah has improper detection of disallowed URIs via `allowed_uri?`
IDs: GHSA-2j22-pr5w-6gq8
Record: https://patchnext.com/advisories/ghsa-2j22-pr5w-6gq8 (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: 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 2.25.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems loofah: affected >= 2.25.0, <= 2.25.0; fixed in 2.25.1

## 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-2j22-pr5w-6gq8 (GitHub-reviewed advisory GHSA-2j22-pr5w-6gq8 lists affected ranges: RubyGems loofah >=2.25.0 <=2.25.0)

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