CVE-2026-3520
DoS in Multer via malformed multipart requests; upgrade to 2.1.1.
Is CVE-2026-3520 being exploited?
Not confirmed. CVE-2026-3520 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 0.71% probability of exploitation in the next 30 days.
How severe is CVE-2026-3520?
CVE-2026-3520 is rated High with a CVSS score of 8.7. 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-2026-3520?
Yes. A fix has been recorded for CVE-2026-3520. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-3520 affect?
CVE-2026-3520 affects Multer (Node.js middleware) <=2.0.x. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-3520?
Upgrade to 2.1.1 and verify all upload endpoints.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Denial of service: processing malformed multipart/form-data may crash Node.js apps via stack overflow.
Patch when possible
- affected< 2.1.1
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.