CVE-2026-97151Hinoki check available

Prototype pollution via document-supplied style identifiers

Published Sep 24, 2026 · Updated Sep 24, 2026

Prototype pollution in Mammoth.js before 1.12.2 allows attackers to modify Object.prototype by converting a crafted DOCX file. The styles reader stores document-supplied style identifiers as keys in ordinary JavaScript objects, allowing a proto identifier to mutate Object.prototype. In 1.11.0 through 1.12.1, a process that enables externalFileAccess, converts another document in the polluted process, and returns its HTML also exposes local file contents to the document supplier.

CVSS severityUnavailable
Unscored
EPSS probability0.36%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Prototype pollution in Mammoth.js before 1.12.2 allows attackers to modify Object.prototype by converting a crafted DOCX file. The styles reader stores document-supplied style identifiers as keys in ordinary JavaScript objects, allowing a proto identifier to mutate Object.prototype. In 1.11.0 through 1.12.1, a process that enables externalFileAccess, converts another document in the polluted process, and returns its HTML also exposes local file contents to the document supplier.

The record

CVE
CVE-2026-97151
Published
Sep 24, 2026
Updated
Sep 24, 2026
Vendor
Michael Williamson
Product
Mammoth.js
Classifications
Unavailable
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Sep 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=0 <1.12.2

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Michael Williamson · Mammoth.jsversion=0 <1.12.2

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

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No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

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Technologies

Your stack

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