CVE-2026-33979
Express XSS Sanitizer bypasses empty config, enabling XSS.
Is CVE-2026-33979 being exploited?
Not confirmed. CVE-2026-33979 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.38% probability of exploitation in the next 30 days.
How severe is CVE-2026-33979?
CVE-2026-33979 is rated High with a CVSS score of 8.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-33979?
Yes. A fix has been recorded for CVE-2026-33979. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-33979 affect?
CVE-2026-33979 affects Express XSS Sanitizer middleware <2.0.2, Express 4.x/5.x apps using this middleware. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-33979?
Upgrade to 2.0.2+; review sanitizer config usage.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Bypass sanitization; attacker can inject XSS via user inputs (body/query/headers/params) in apps using the middleware.
Patch when possible
- affected< 2.0.2
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.