Vulnerability · Published Aug 12, 2026 · Assigned by GitHub_M

CVE-2026-73491Loofah `allowed_uri?` does not detect `javascript:` URIs split by named whitespace character references

Low 2.3

In plain English

A low-severity security flaw in loofah from flavorjones. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 34% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)2.3Low

Exploit odds (30 days)0.4%top 66.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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 &Tab; or &NewLine;. 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	ruby-loofah	no fix listed	DEBIAN-CVE-2026-73491
Debian:13	ruby-loofah	no fix listed	DEBIAN-CVE-2026-73491
Debian:14	ruby-loofah	2.25.2-1	DEBIAN-CVE-2026-73491
RubyGems	loofah	2.25.2	GHSA-8whx-365g-h9vv
Ubuntu:22.04:LTS	ruby-loofah	no fix listed	UBUNTU-CVE-2026-73491
Ubuntu:24.04:LTS	ruby-loofah	no fix listed	UBUNTU-CVE-2026-73491
Ubuntu:26.04:LTS	ruby-loofah	no fix listed	UBUNTU-CVE-2026-73491
Ubuntu:26.10	ruby-loofah	no fix listed	UBUNTU-CVE-2026-73491

Affected products (as reported)

Vendor	Product	Versions
flavorjones	loofah	>= 2.25.0, < 2.25.2

Weakness: CWE-184 · Vector: 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

References

https://github.com/flavorjones/loofah/security/advisories/GHSA-8whx-365g-h9vv x_refsource_CONFIRM
https://github.com/flavorjones/loofah/pull/308 x_refsource_MISC
https://github.com/flavorjones/loofah/commit/5e91af861e3cdab47b91dd0b81f3afdfd13a5e19 x_refsource_MISC
https://github.com/flavorjones/loofah/releases/tag/v2.25.2 x_refsource_MISC