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Fencer Vulns
low 2.3

CVE-2026-73491 json

Loofah `allowed_uri?` does not detect `javascript:` URIs split by named whitespace character references

published 2026-07-21 3 mo ago modified 2026-10-24 15 d ago also GHSA-8whx-365g-h9vv , EUVD-2026-57628

cvss
2.3
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 33%
public exploits
0
none known

Summary

Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.25.0 until 2.25.2, Loofah::HTML5::Scrub.allowed_uri? does not reject javascript: URIs whose scheme is split or prefixed with the HTML5 named whitespace character references 	 or 
. CGI.unescapeHTML leaves those references intact, so allowed_uri? reports the URL safe even though a browser decodes and strips the tab or line feed and executes the resulting javascript: URL. This issue affects only callers that pass HTML-encoded strings directly to allowed_uri?; Loofah's default sanitize() path is not affected. This issue is fixed in version 2.25.2.

Patch / fix

  • rubygems loofah 2.25.2
  • ruby-loofah Debian 14 2.25.2-1

debian advisories DEBIAN-CVE-2026-73491

  • hawk2 SLE High Availability Extension 16.0, SLES for SAP applications 16.0 2.7.2+git.1788518533.7d4dadd6-160000.1.1

suse advisories SUSE-SU-2026:24195-1SUSE-SU-2026:24250-1

  • hawk2 openSUSE Tumbleweed 2.7.2+git.1792148770.648dcddb-1.1
  • hawk2 openSUSE Leap 16.0 2.7.2+git.1788518533.7d4dadd6-160000.1.1

opensuse advisories openSUSE-SU-2026:12153-1openSUSE-SU-2026:22068-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-73491 updated cvss 3.7

rubygem-loofah: Loofah: Cross-Site Scripting via malformed `javascript:` URI parsing

  • Red Hat 3scale API Management Platform 2 3scale-amp2/zync-rhel9, 3scale-amp2/system-rhel8
    affected: no fix planned “Out of support scope”
  • Red Hat Satellite 6 rubygem-loofah 2.25.0-1.el9sat
    affected: no fix available “Fix deferred”
  • Red Hat 3scale API Management Platform 2 3scale-amp2/system-rhel9 Red Hat Satellite 6 tfm-rubygem-graphql, rubygem-loofah 2.22.0-1.el8sat
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 mo ago

Exploit prediction

0.39% chance of exploitation in the next 30 days, higher than 33% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 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
CNA 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
rubygems loofah
>=2.25.0, <2.25.2
2.25.2

Affected products

  • flavorjones loofah

Classification

Weakness
  • CWE-184 Incomplete List of Disallowed Inputs

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.