Cross-site scripting in Loofah - #VU128121
Published: April 27, 2026
Vulnerability identifier: #VU128121
CSH Severity: Medium
CVSS v4: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N]
CVE-ID: N/A
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to perform cross-site scripting.
The vulnerability exists due to improper input validation in Loofah::HTML5::Scrub.allowed_uri? when processing HTML-encoded user-supplied URIs. A remote attacker can supply a specially crafted URI to perform cross-site scripting.
This issue only affects direct callers of the string-level helper with HTML-encoded strings; the default sanitize() path is not affected.
Affected software
Loofah
Remediation
Install security update from vendor's website.
Loofah - update to 2.25.1