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Fencer Vulns
high 7.5

CVE-2026-5079 json

multer vulnerable to Denial of Service via deeply nested field names

published 2026-06-15 4 mo ago modified 2026-06-17 4 mo ago also GHSA-72gw-mp4g-v24j , EUVD-2026-36726

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 20%
public exploits
0
none known

Summary

Impact: multer versions 1.0.0 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service via deeply nested field names in multipart form data. The append-field dependency parses bracket notation in field names with no limit on nesting depth, allowing an attacker to force allocation of deeply nested object structures that consume CPU and memory. A single HTTP request with a crafted multipart body is sufficient to exploit this.

Patches: Users should upgrade to multer 2.2.0 (2.x line) or 3.0.0-alpha.2 (3.x prerelease) and configure the new limits.fieldNestingDepth option to the minimum depth their application requires.

Workarounds: Set limits.fields to a reasonable value to reduce the number of fields an attacker can send per request. This does not fully mitigate the issue but limits the impact.

Patch / fix

  • npm multer 2.2.0, 3.0.0-alpha.2
  • multer multer 2.2.0, 3.0.0-alpha.2

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-5079 updated cvss 7.5

multer: Multer: Denial of Service via deeply nested field names in multipart form data

  • Red Hat Logging Subsystem for Red Hat OpenShift openshift-logging/vector-rhel9
    affected: workaround, no fix available
  • Red Hat Ansible Automation Platform 2.1 ansible-automation-platform/automation-portal 1788775748
    fixed: vendor fix RHSA-2026:65118
  • Red Hat Ansible Automation Platform 2.2 ansible-automation-platform/bootc-automation-portal-rhel9 1788943531
    fixed: vendor fix RHSA-2026:66003
  • Red Hat Developer Hub 1.9 rhdh/rhdh-hub-rhel9 1785972843
    fixed: vendor fix RHSA-2026:52768
  • Red Hat Developer Hub 1.10 rhdh/rhdh-hub-rhel9 1785411652, rhdh/red-hat-developer-hub-backstage-plugin-lightspeed-backend 1785332487, rhdh/red-hat-developer-hub-backstage-plugin-orchestrator-backend 1785332825
    fixed: vendor fix RHSA-2026:48126
  • Red Hat Developer Hub 1.9 rhdh/rhdh-rhel9-operator 1785972533, rhdh/rhdh-operator-bundle 1785976147 Red Hat Developer Hub 1.10 rhdh/rhdh-rhel9-operator 1785411290, rhdh/rhdh-operator-bundle 1785415596, rhdh/rhdh-must-gather-rhel9 1784202439, rhdh/rhdh-rag-content-rhel9 1785162496, rhdh/red-hat-developer-hub-backstage-plugin-lightspeed 1785333413, rhdh/red-hat-developer-hub-backstage-plugin-orchestrator 1785340831, +3 more
    not affected: vulnerable code not present
  • Red Hat Enterprise Linux 7 firefox Red Hat Enterprise Linux 8 thunderbird Red Hat Enterprise Linux 9 firefox, firefox-x11, thunderbird
    not affected: vulnerable code not in execute path
  • Red Hat Enterprise Linux 10 firefox, thunderbird, fido-device-onboard Red Hat Trusted Profile Analyzer rhtpa/rhtpa-trustification-service-rhel9
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.28% chance of exploitation in the next 30 days, higher than 20% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
npm multer
>=1.0.0, <2.2.0
>=3.0.0-alpha.1, <3.0.0-alpha.2
2.2.0
3.0.0-alpha.2

Affected products

  • multer multer

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.