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CVE Record

CVE-2026-3304: Multer vulnerable to Denial of Service via incomplete cleanup

Multer is a node.js middleware for handling `multipart/form-data`. A vulnerability in Multer prior to version 2.1.0 allows an attacker to trigger a Denial of Service (DoS) by sending malformed requests, potentially causing resource exhaustion. Users should upgrade to version 2.1.0 to receive a patch. No known workarounds are available.

HighCVSS 8.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Multer, a Node.js upload-handling middleware, can be forced by malformed multipart requests into a denial-of-service condition before version 2.1.0. The business risk is service availability: public file-upload paths may consume resources and stop responding. The source bundle names an upgrade to 2.1.0 and says no known workarounds are available.

Executive priority

Treat this as a high-priority availability issue for customer-facing upload services. Patch quickly where Multer is present, starting with internet-facing systems and business-critical applications. No source-provided workaround means version remediation is the primary path.

Technical view

CVE-2026-3304 is a CWE-459 incomplete cleanup flaw in expressjs Multer before 2.1.0. The CVSS 4.0 score is 8.7, with network attack vector, low complexity, no privileges, no user interaction, and high vulnerable-system availability impact. Sources describe malformed requests causing resource exhaustion through incomplete cleanup.

Likely exposure

Most likely exposure is internet-facing Node.js or Express applications using Multer before 2.1.0 to process multipart/form-data, especially file-upload endpoints. Applications without upload routes or not using Multer are not indicated as affected by the provided sources.

Exploitation context

The source bundle does not show CISA KEV listing or cited evidence of active exploitation. The vulnerability is still operationally serious because the CVSS vector indicates unauthenticated, network-reachable denial of service with low attack complexity.

Researcher notes

The evidence supports a denial-of-service analysis, not confidentiality or integrity compromise. The affected condition is tied to malformed multipart handling and incomplete cleanup. The provided affected-product metadata is sparse, so researchers should validate actual dependency versions in each application rather than relying only on product names.

Mitigation direction

  • Upgrade Multer to version 2.1.0 or later.
  • Rebuild and redeploy applications after dependency updates.
  • Check vendor advisories for packaged or downstream Multer copies.
  • Do not rely on workarounds; the bundle says none are known.
  • Prioritize public upload services and critical customer workflows.

Validation and detection

  • Inventory applications using the multer package.
  • Confirm dependency lockfiles resolve Multer to 2.1.0 or later.
  • Identify routes accepting multipart/form-data uploads.
  • Verify deployed containers or bundles include the patched dependency.
  • Review Red Hat advisories if using Red Hat-packaged components.
Prepared
Confidence
high
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-459: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2026-3304 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.7 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
10Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.7CVSS 4.0HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N——openjs
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 4.0 score

8.7High
CVSS 4.0 vector shape for CVE-2026-3304Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPmulter: Multer: Denial of Service via malformed requests
other:Red Hat severity ratingcvssV3_1
  • 2026-02-27T16:01:39.674Z: Reported to Red Hat.
  • 2026-02-27T15:44:37.187Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
expressjsmulter0.0.0unaffected
Weakness

CWE details

CWE-459

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-459 · source CWE mapping

Incomplete Cleanup

Incomplete Cleanup represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs