GHSA-46fp-8f5p-pf2m
Improper detection of disallowed URIs by Loofah `allowed_uri?`
Summary
Loofah::HTML5::Scrub.allowed_uri? 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 allowed_uri? 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 allowed_uri? string-level helper when passing HTML-encoded strings.
Impact
Applications that call Loofah::HTML5::Scrub.allowed_uri? 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 Loofah 2.25.0.
Mitigation
Upgrade to Loofah >= 2.25.1.
Credit
Responsibly reported by HackOne user @smlee.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- None
What each source reports
GitHub Advisories Score used
Improper detection of disallowed URIs by Loofah `allowed_uri?`
Summary
Loofah::HTML5::Scrub.allowed_uri? 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 allowed_uri? 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 allowed_uri? string-level helper when passing HTML-encoded strings.
Impact
Applications that call Loofah::HTML5::Scrub.allowed_uri? 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 Loofah 2.25.0.
Mitigation
Upgrade to Loofah >= 2.25.1.
Credit
Responsibly reported by HackOne user @smlee.
- Record
GHSA-46fp-8f5p-pf2m- CVSS 4.0
- 2.7 Low
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U - Weakness
- CWE-79
- Updated
- 2026-11-02
OSV
Improper detection of disallowed URIs by Loofah `allowed_uri?`
Summary
Loofah::HTML5::Scrub.allowed_uri? 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 allowed_uri? 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 allowed_uri? string-level helper when passing HTML-encoded strings.
Impact
Applications that call Loofah::HTML5::Scrub.allowed_uri? 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 Loofah 2.25.0.
Mitigation
Upgrade to Loofah >= 2.25.1.
Credit
Responsibly reported by HackOne user @smlee.
- Record
GHSA-46fp-8f5p-pf2m- CVSS 4.0
- 2.7 Low
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U - Weakness
- CWE-79
- Updated
- 2026-11-02
Affected packages
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | GitHub Advisories, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
GHSA-46fp-8f5p-pf2m is a low vulnerability (CVSS 2.7) in loofah, published March 18, 2026. No source lists public exploit code. Fixed in loofah 2.25.1.