CVE-2026-97151

Prototype Pollution in mammoth.js via Malicious DOCX

Published Sep 24, 2026 CVSS 4.0 · 8.4 High EPSS < 1% KEV · Not listed
Description
mammoth (aka mammoth.js) before 1.12.2 is vulnerable to prototype pollution when reading the styles defined in a document. Converting a crafted .docx file allows an attacker to add arbitrary properties to Object.prototype. In 1.11.0 through 1.12.1, applications that convert further documents in the same process and return the converted HTML can also disclose the contents of local server files (to the party supplying the documents) by setting externalFileAccess to true.

Remediation

Vendor Solution

Upgrade to mammoth 1.12.2 or later.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Mwilliamson
Mwilliamson mammoth.js
Vendors & Products Mwilliamson
Mwilliamson mammoth.js
Type Values Removed Values Added
Title Prototype Pollution in mammoth.js via Malicious DOCX
Type Values Removed Values Added
Description mammoth (aka mammoth.js) before 1.12.2 is vulnerable to prototype pollution when reading the styles defined in a document. Converting a crafted .docx file allows an attacker to add arbitrary properties to Object.prototype. In 1.11.0 through 1.12.1, applications that convert further documents in the same process and return the converted HTML can also disclose the contents of local server files (to the party supplying the documents) by setting externalFileAccess to true.
Weaknesses CWE-1321
References
Metrics cvssV4_0

{'score': 8.4, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:L/VA:H/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
mitre
Published
Updated
Sep 24, 2026, 1:02 PM
Reserved
Sep 24, 2026, 3:08 AM
Status
Awaiting Analysis
Published
Sep 24, 2026, 4:18 AM
Modified
Sep 24, 2026, 9:04 PM