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CVE-2026-3520

Multer vulnerable to Denial of Service via uncontrolled recursion

8.7 HighFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.82%Up 0.8 points since Mar 5, 2026
90%50%10%1%

What each source reports

CVE List Score used 8.7

Multer vulnerable to Denial of Service via uncontrolled recursion

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.

Record
CVE-2026-3520
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-674, CWE-770
Updated
2026-11-02
EUVDEUVD-2026-9423 8.7

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.

Record
EUVD-2026-9423
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-5528-5vmv-3xc2 8.7

Multer Vulnerable to Denial of Service via Uncontrolled Recursion

Impact

A vulnerability in Multer versions < 2.1.1 allows an attacker to trigger a Denial of Service (DoS) by sending malformed requests, potentially causing stack overflow.

Patches

Users should upgrade to 2.1.1

Workarounds

None

Resources

Record
GHSA-5528-5vmv-3xc2
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-674
Updated
2026-11-02
NVD 8.7

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.

Record
CVE-2026-3520
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-674, CWE-770
Updated
2026-11-02
OSV 8.7

Multer vulnerable to Denial of Service via uncontrolled recursion

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.

Record
CVE-2026-3520
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-674
Updated
2026-11-02
OSVGHSA-5528-5vmv-3xc2 8.7

Multer Vulnerable to Denial of Service via Uncontrolled Recursion

Impact

A vulnerability in Multer versions < 2.1.1 allows an attacker to trigger a Denial of Service (DoS) by sending malformed requests, potentially causing stack overflow.

Patches

Users should upgrade to 2.1.1

Workarounds

None

Resources

Record
GHSA-5528-5vmv-3xc2
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-674
Updated
2026-11-02
OSVROOT-APP-NPM-CVE-2026-3520 No score

CVE-2026-3520 in multer - Patched by Root

Root has patched CVE-2026-3520 in the multer package for Root:npm. Multiple fixed versions available.

Record
ROOT-APP-NPM-CVE-2026-3520
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
multer
npm
 before 2.1.1
2.1.1
multer
Root:npm
 before 1.4.4-lts.1-aikido.3
1.4.4-lts.1-aikido.31.4.5-lts.2-aikido.91.4.4-lts.1-aikido.41.4.4-aikido.21.4.2-aikido.12.0.2-aikido.41.4.5-lts.1-aikido.21.4.5-lts.1-aikido.32.0.2-aikido.52.0.2-aikido.61.4.4-aikido.31.4.4-lts.1-aikido.11.4.4-aikido.41.4.5-lts.1-aikido.11.4.4-lts.1-aikido.21.4.4-aikido.51.4.4-aikido.61.4.2-aikido.21.4.5-lts.2-aikido.71.4.5-lts.2-aikido.82.1.1-aikido.42.0.2-aikido.72.1.1-aikido.32.1.1-aikido.12.1.1-aikido.2
@rootio/multer
Root:npm
 before 1.4.4-lts.1-root.io.3
1.4.4-lts.1-root.io.31.4.5-lts.2-root.io.92.0.2-root.io.12.0.2-root.io.22.0.2-root.io.31.4.4-lts.1-root.io.41.4.4-root.io.21.4.4-root.io.11.4.2-root.io.12.0.2-root.io.41.4.5-lts.1-root.io.21.4.5-lts.1-root.io.32.0.2-root.io.52.0.2-root.io.61.4.4-root.io.31.4.4-lts.1-root.io.11.4.4-root.io.41.4.5-lts.1-root.io.11.4.4-lts.1-root.io.21.4.4-root.io.51.4.4-root.io.61.4.2-root.io.21.4.5-lts.2-root.io.71.4.5-lts.2-root.io.82.1.1-root.io.42.0.2-root.io.72.1.1-root.io.32.1.1-root.io.12.1.1-root.io.2

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-3520 is a high vulnerability (CVSS 8.7) in Expressjs Multer, published March 4, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.82%, the 57th percentile. Fixed in multer 2.1.1.

References

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