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CVE-2026-33979

Express Xss Sanitizer Project Express Xss Sanitizer cross-site scripting (XSS)

8.2 HIGHPublic exploitEPSS 0.42%
  1. Published27 Mar 2026

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 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityLow
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N

Affected products

Express Xss Sanitizer Project Express Xss Sanitizer< 2.0.2

Remediation

Fixed in
Express Xss Sanitizer Project Express Xss Sanitizer≥ 2.0.2

References

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Frequently asked

Is CVE-2026-33979 being actively exploited?

CVE-2026-33979 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.42%.

How severe is CVE-2026-33979?

CVE-2026-33979 has a CVSS 3.1 base score of 8.2, rated high. EPSS estimates a 0.42% probability of exploitation.

Which products are affected by CVE-2026-33979?

Affected products include Express Xss Sanitizer Project Express Xss Sanitizer.

How do I fix CVE-2026-33979?

Upgrade affected software to a fixed version, for example Express Xss Sanitizer Project Express Xss Sanitizer 2.0.2 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-33979 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.