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PatchSiren cyber security CVE debrief

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
2026-06-16
Advisory published
2026-06-15
Advisory updated
2026-06-16

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.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-5038 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-5038

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-5038 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-5038

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source reference

    Unverified legacy reference

    URL: https://cna.openjsf.org/security-advisories.html

    ce714d77-add3-4f53-aff5-83d477b104bb

  • Source reference

    Unverified legacy reference

    URL: https://github.com/expressjs/multer/security/advisories/GHSA-3p4h-7m6x-2hcm

    ce714d77-add3-4f53-aff5-83d477b104bb

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.