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CVE-2026-5038 multer CVE debrief

CVE-2026-5038 is a Denial of Service vulnerability affecting multer versions 2.0.0-alpha.1 through 2.1.1 and 3.0.0-alpha.1. The vulnerability occurs when using diskStorage, where aborted or malformed multipart uploads leave orphaned partial files on disk. This happens because the Readable.pipe() call does not propagate the stream destroy signal to the underlying fs.WriteStream. An attacker can exploit this by triggering many aborted uploads, leading to disk space exhaustion, without requiring any application bug.

Vendor
multer
Product
Unknown
CVSS
MEDIUM 5.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-15
Original CVE updated
2026-06-15
Advisory published
2026-06-15
Advisory updated
2026-06-15

Who should care

Users of multer versions 2.0.0-alpha.1 through 2.1.1 and 3.0.0-alpha.1 should be aware of this vulnerability and take necessary actions to mitigate it.

Technical summary

The vulnerability has a CVSS score of 5.3 and is classified as MEDIUM severity. It can be exploited by an attacker to cause a Denial of Service by exhausting disk space through triggered aborted uploads.

Defensive priority

High

Recommended defensive actions

  • Upgrade to multer version 2.2.0 (for 2.x line) or 3.0.0-alpha.2 (for 3.x prerelease) as these versions track in-flight write streams and clean them up on the abort path.

Evidence notes

The CVE record was published on June 15, 2026, and has not been modified since then. The vulnerability was reported by an unknown vendor, and Openjsf is listed as a candidate for the reference domain.

Official resources

CVE-2026-5038 was published on 2026-06-15T16:16:34.423Z.