Vulnerability Details CVE-2026-77078
multer is a middleware for handling multipart/form-data in Node.js. A small multipart request containing two specially crafted text field names can cause an uncaught RangeError (Invalid array length) that terminates the Node.js process. The first field uses a very large numeric array index to allocate a maximum-length sparse array, and a second field then pushes past that length, which throws inside the append-field dependency and is not caught by multer. All versions before 2.3.0 are affected, and the issue is a remotely triggerable denial of service. The issue is fixed in multer 2.3.0. Upgrade to multer 2.3.0 to remediate.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.003
EPSS Ranking 21.2%
CVSS Severity
CVSS v3 Score 7.5
References
Products affected by CVE-2026-77078
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cpe:2.3:a:expressjs:multer:1.0.0
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cpe:2.3:a:expressjs:multer:1.0.1
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cpe:2.3:a:expressjs:multer:1.0.2
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cpe:2.3:a:expressjs:multer:1.0.3
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cpe:2.3:a:expressjs:multer:1.0.4
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cpe:2.3:a:expressjs:multer:1.0.5
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cpe:2.3:a:expressjs:multer:1.0.6
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cpe:2.3:a:expressjs:multer:1.1.0
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cpe:2.3:a:expressjs:multer:1.2.0
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cpe:2.3:a:expressjs:multer:1.2.1
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cpe:2.3:a:expressjs:multer:1.3.0
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cpe:2.3:a:expressjs:multer:1.3.1
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cpe:2.3:a:expressjs:multer:1.4.0
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cpe:2.3:a:expressjs:multer:1.4.1
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cpe:2.3:a:expressjs:multer:1.4.2
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cpe:2.3:a:expressjs:multer:1.4.3
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cpe:2.3:a:expressjs:multer:1.4.4
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cpe:2.3:a:expressjs:multer:1.4.5
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cpe:2.3:a:expressjs:multer:2.0.0
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cpe:2.3:a:expressjs:multer:2.0.1
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cpe:2.3:a:expressjs:multer:2.0.2
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cpe:2.3:a:expressjs:multer:2.1.0
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cpe:2.3:a:expressjs:multer:2.1.1
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cpe:2.3:a:expressjs:multer:2.2.0