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

Quick assessment

Affected
flavorjones loofah
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Mike Dalessio Loofah是Mike Dalessio个人开发者开源的一款HTML文档处理组件。 flavorjones loofah 2.25.0版本至2.25.2之前版本存在输入验证错误漏洞，该漏洞源于输入验证不当，allowed_uri?未拒绝带有HTML5命名空白字符引用（	或
）的javascript: URI，可能导致浏览器执行恶意javascript代码。

CVSS 2.3 · Low EPSS 0.39% · P31

Possible ATT&CK Techniques 1 AI

T1189 · Drive-by Compromise

Affected Version Matrix 1

VendorProduct Version RangeStatus
flavorjones loofah >= 2.25.0, < 2.25.2 affected
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I. Basic Information for CVE-2026-73491

Vulnerability Information
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Vulnerability Title
Loofah `allowed_uri?` does not detect `javascript:` URIs split by named whitespace character references
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
不完整的黑名单
Source: CVE Program / CVE List V5
Vulnerability Title
flavorjones loofah 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mike Dalessio Loofah是Mike Dalessio个人开发者开源的一款HTML文档处理组件。 flavorjones loofah 2.25.0版本至2.25.2之前版本存在输入验证错误漏洞，该漏洞源于输入验证不当，allowed_uri?未拒绝带有HTML5命名空白字符引用（&Tab;或&NewLine;）的javascript: URI，可能导致浏览器执行恶意javascript代码。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
flavorjones loofah >= 2.25.0, < 2.25.2 -

II. Public POCs for CVE-2026-73491

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III. Intelligence Information for CVE-2026-73491

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Patches & Fixes for CVE-2026-73491 (2)

Vendor Advisories for CVE-2026-73491 (1)

Vendor Pages for CVE-2026-73491 (1)

Same Patch Batch · flavorjones · 2026-08-12 · 3 CVEs total

CVE-2026-73490 4.7 MEDIUM Loofah: SVG `href` attribute bypasses local-reference restriction
CVE-2026-73492 2.3 LOW Loofah `allowed_uri?` does not detect `javascript:` URIs split by numeric character refere

IV. Related Vulnerabilities

Same product: loofah
Same vendor: flavorjones
Same weakness: CWE-184

V. Comments for CVE-2026-73491

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