Cross-site scripting in Loofah - CVE-2026-126209
Published: November 8, 2026 / Updated: November 13, 2026
Vulnerability identifier: #VU161890
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: CVE-2026-126209
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows an unauthenticated remote attacker to execute JavaScript in a victim's browser through applications using Loofah's URI validation helper.
The vulnerability exists due to Loofah's allowed_uri? helper stripping whitespace before decoding semicolon-less numeric character references when called directly with HTML-encoded URLs. An unauthenticated remote attacker can submit an encoded script URL that passes validation and executes when rendered in a browser-interpreted URI attribute and activated by a victim.
Affected software
Loofah
How to mitigate CVE-2026-126209
Install security update from vendor's website.
Loofah - update to 2.25.3