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CVE Record

CVE-2026-3520: Multer vulnerable to Denial of Service via uncontrolled recursion

Multer is a node.js middleware for handling `multipart/form-data`. A vulnerability in Multer prior to version 2.1.1 allows an attacker to trigger a Denial of Service (DoS) by sending malformed requests, potentially causing stack overflow. Users should upgrade to version 2.1.1 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 common Node.js file-upload middleware, can be crashed by malformed multipart requests in versions before 2.1.1. The business risk is service disruption for applications that accept uploads. The sources name a patched version and no workaround.

Executive priority

Prioritize remediation in the next standard security release cycle, faster for public upload services. The issue does not expose data in the supplied sources, but it can interrupt service without authentication and has a high availability score.

Technical view

CVE-2026-3520 is an uncontrolled recursion/resource exhaustion issue in Multer before 2.1.1. A remote unauthenticated attacker can send malformed multipart/form-data that may trigger stack overflow and denial of service. CVSS v4 is 8.7 with high availability impact only.

Likely exposure

Exposure is most likely in Node.js/Express applications using Multer before 2.1.1 on upload or multipart/form-data endpoints, especially internet-facing services. Red Hat references exist, but the supplied bundle does not provide enough detail to generalize affected Red Hat product scope.

Exploitation context

The vulnerability is network reachable, low complexity, requires no privileges, and needs no user interaction. The bundle says KEV is false and provides no cited evidence of active exploitation. Treat it as plausible to exploit for availability disruption, not confirmed exploited in the wild.

Researcher notes

The supplied affected-product metadata is sparse and appears less informative than the narrative advisory, which says Multer before 2.1.1 is vulnerable. Validate against the GitHub advisory, CVE record, commit, and vendor-specific Red Hat records before scoping downstream packages.

Mitigation direction

  • Upgrade Multer to version 2.1.1 or later.
  • Apply relevant Red Hat errata where Red Hat-packaged software is in scope.
  • Prioritize internet-facing upload endpoints using multipart/form-data.
  • If upgrade timing is constrained, check vendor guidance; sources name no workaround.

Validation and detection

  • Inventory package manifests and lockfiles for Multer versions below 2.1.1.
  • Map all upload routes and services accepting multipart/form-data.
  • Confirm deployed containers and build artifacts include Multer 2.1.1 or later.
  • Review Red Hat CVE, VEX, and errata records for product applicability.
  • Monitor availability metrics for crashes around malformed upload requests.
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-674: 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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cwe · low confidence lookup

CWE-770: 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-2026-3520 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-2026-3520Attack 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
  • 2026-03-04T17:01:43.432Z: Reported to Red Hat.
  • 2026-03-04T16:17:18.962Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
expressjsmulter0unaffected
Weakness

CWE details

CWE-674CWE-770

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