What’s Vulnerable › Vulnerabilities

CVE-2026-97151

• Severity: high (CVSS 8.4 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-24 · updated 2026-09-24
• Weakness: CWE-1321

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.

Affected products

• mwilliamson mammoth.js: before 1.12.2 — fixed in 1.12.2

How to fix

Upgrade to a fixed version: mwilliamson mammoth.js 1.12.2. Check the vendor advisory for mitigations.

References

• https://github.com/mwilliamson/mammoth.js/commit/2888fa158d67c1419199f152326e12a05618b53e
• https://github.com/mwilliamson/mammoth.js/commit/31f0c370be4b95ac4fa285fea3be970606735f16
• https://raw.githubusercontent.com/mwilliamson/mammoth.js/master/NEWS
• https://www.npmjs.com/package/mammoth

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