How severe is CVE-2026-3520?

CVE-2026-3520 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-3520 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-3520?

CVE-2026-3520 affects Expressjs Multer. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-3520?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-3520 have an EU (EUVD) identifier?

Yes. CVE-2026-3520 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-9423.

When was CVE-2026-3520 published?

CVE-2026-3520 was published on 2026-03-04 and last updated on 2026-06-30.

CVE-2026-3520

CVE-2026-3520 is a high-severity vulnerability in Expressjs Multer with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-674.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 8.7
EPSS exploit prediction: 1% (49th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-9423
Weakness: CWE-674
Affected product: Expressjs Multer
Published: 2026-03-04
Last modified: 2026-06-30

Description

Multer is a node.js middleware for handling `multipart/form-data`. A vulnerability in Multer prior to version 2.1.1 allows an attacker to trigger a Denial of Service (DoS) by sending malformed requests, potentially causing stack overflow. Users should upgrade to version 2.1.1 to receive a patch. No known workarounds are available.

Frequently asked questions

What is CVE-2026-3520?: Multer is a node.js middleware for handling `multipart/form-data`. A vulnerability in Multer prior to version 2.1.1 allows an attacker to trigger a Denial of Service (DoS) by sending malformed requests, potentially causing stack overflow. Users should upgrade to version 2.1.1 to receive a patch. No known workarounds are available.
How severe is CVE-2026-3520?: CVE-2026-3520 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-3520 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-3520?: CVE-2026-3520 affects Expressjs Multer. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-3520?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-3520 have an EU (EUVD) identifier?: Yes. CVE-2026-3520 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-9423.
When was CVE-2026-3520 published?: CVE-2026-3520 was published on 2026-03-04 and last updated on 2026-06-30.

References

Affected products (1)

cpe:2.3:a:expressjs:multer:*:*:*:*:*:node.js:*:*

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CVE-2026-5079 — High (CVSS 7.5): Impact: multer versions 1.0.0 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service via deeply nested…
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