CVE-2026-33979: Express Xss Sanitizer Project Express Xss Sanitizer

High severity, CVSS 8.2. EPSS: 0.4% chance of exploitation in the next 30 days.

Express XSS Sanitizer is Express 4.x and 5.x middleware which sanitizes user input data (in req.body, req.query, req.headers and req.params) to prevent Cross Site Scripting (XSS) attack. A vulnerability has been identified in versions prior to 2.0.2 where restrictive sanitization configurations are silently ignored. In version 2.0.2, the validation logic has been updated to respect explicitly provided empty configurations. Now, if allowedTags or allowedAttributes are provided (even if empty), they are passed directly to sanitize-html without being overridden.

Affected products

• Express Xss Sanitizer Project Express Xss Sanitizer: before 2.0.2 (fixed in 2.0.2)

Published 2026-03-27. Last modified 2026-06-17.