CVE-2026-5079
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk19th percentile — higher than 19% of all known CVEs
Summary
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 field names in multipart form data. An attacker can exploit this to force allocation of deeply nested object structures, consuming CPU and memory.
Risk Assessment
The organization may experience significant performance issues, potentially leading to service unavailability. An attacker can leverage this vulnerability to conduct a DoS attack using a single crafted HTTP request.
Recommendation
It is recommended to upgrade to multer version 2.2.0 or 3.0.0-alpha.2 and configure the limits.fieldNestingDepth option to the minimum depth required by the application. Additionally, setting limits.fields to a reasonable value can help limit the number of fields an attacker can send per request.
Original NVD description (English source)
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 field names in multipart form data. The append-field dependency parses bracket notation in field names with no limit on nesting depth, allowing an attacker to force allocation of deeply nested object structures that consume CPU and memory. A single HTTP request with a crafted multipart body is sufficient to exploit this. Patches: Users should upgrade to multer 2.2.0 (2.x line) or 3.0.0-alpha.2 (3.x prerelease) and configure the new limits.fieldNestingDepth option to the minimum depth their application requires. Workarounds: Set limits.fields to a reasonable value to reduce the number of fields an attacker can send per request. This does not fully mitigate the issue but limits the impact.