CVE-2026-33979
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.38%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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.
- CVSS 3.1
- 8.2 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
- EPSS
- 0.38% probability · 32th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-79, CWE-183
- Affected
- express xss sanitizer project/express xss sanitizer
- Source
- security-advisories@github.com
References
- https://github.com/AhmedAdelFahim/express-xss-sanitizer/commit/5623009ef11dcf095c163a38dea07b9cc22ad19fPatch
- https://github.com/AhmedAdelFahim/express-xss-sanitizer/releases/tag/v2.0.2Product, Release Notes
- https://github.com/AhmedAdelFahim/express-xss-sanitizer/security/advisories/GHSA-3843-rr4g-m8jqExploit, Mitigation, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.