Cyber Resilience

CVE-2026-3304

Expressjs Multer ≤ 2.1.0

Published
27 February 2026
Modified
15 July 2026
Patch / advisory
View advisory
CVSS Score v4 8.7
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0066 48th percentile
Risk Priority 45 floored blend · peak EPSS

Summary

CVE-2026-3304 is a high-severity Incomplete Cleanup (CWE-459) vulnerability in Expressjs Multer. Its CVSS base score is 8.7 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Data from Local System (T1005); ranked at the 48th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-14 (Non-persistence) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-3304 is a vulnerability in Multer, a Node.js middleware used for handling multipart/form-data, affecting versions prior to 2.1.0. It enables attackers to trigger a Denial of Service (DoS) by sending malformed requests, which can lead to resource exhaustion. The issue is classified under CWE-459 and carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

An unauthenticated attacker with network access can exploit this vulnerability with low attack complexity and no user interaction required. Exploitation involves crafting and sending malformed multipart/form-data requests to a vulnerable Multer instance, resulting in high-impact disruption to availability through resource exhaustion, while confidentiality and integrity remain unaffected.

Advisories, including those from the OpenJSF CNA and GitHub security notices, recommend upgrading to Multer version 2.1.0, which patches the issue via a specific commit. No known workarounds are available.

EU & UK References

Vulnerability Data

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…

more

to receive a patch. No known workarounds are available.

CWE(s)
CWE-459

Related Threats

MITRE ATT&CK Enterprise Techniques

T1005 Data from Local System Collection
Adversaries may search local system sources, such as file systems, configuration files, local databases, virtual machine files, or process memory, to find files of interest and sensitive data prior to Exfiltration.
attack.mitre.org →
T1552 Unsecured Credentials Credential Access
Adversaries may search compromised systems to find and obtain insecurely stored credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-5038Same product: Expressjs Multer
CVE-2026-3520Same product: Expressjs Multer
CVE-2026-2359Same product: Expressjs Multer
CVE-2026-5079Same product: Expressjs Multer
CVE-2025-66675Shared CWE-459
CVE-2025-2260Shared CWE-459
CVE-2023-31356Shared CWE-459
CVE-2025-60730Shared CWE-459
CVE-2024-50385Shared CWE-459
CVE-2023-41835Shared CWE-459

Affected Assets

expressjs
multer
≤ 2.1.0

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V6.4.1

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation can discover incomplete cleanup through dynamic analysis or resource-leak testing.

SI-14 Non-persistence good match

Non-persistence mechanisms explicitly initiate resources in a known state and terminate them, directly enforcing cleanup.

AC-12 Session Termination partial match

Session termination forces explicit release of session-related temporary resources.

SC-4 Information in Shared System Resources partial match

Preventing unintended information transfer through shared resources requires complete cleanup of those resources.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure-development practices and coding standards normally require proper resource release and cleanup.

ID.AM-08 partial match
prevents

Life-cycle management encompasses disposal of temporary resources but does not specifically target runtime cleanup bugs.

PR.DS-10 partial match
prevents

Explicitly calls for removing sensitive data after use, directly addressing one class of incomplete cleanup.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.10 Information deletion full match
degrades

Explicitly requires secure deletion of temporary or residual data, directly addressing incomplete cleanup.

A.8.25 Secure development life cycle partial match
prevents

SDLC practices include cleanup steps, yet the weakness can still occur if those steps are omitted.

A.8.28 Secure coding partial match
prevents

Secure-coding rules can mandate explicit cleanup of temporary resources, but do not guarantee it.

A.8.32 Change management partial match
finds

Change-management processes may require cleanup verification, but the control itself does not address the weakness.

References