Vulnerability · Published Sep 24, 2026 · Assigned by mitre

CVE-2026-97151

High 8.4

In plain English

A high-severity prototype pollution in mammoth.js from mwilliamson. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 29% of all known vulnerabilities).

Severity (CVSS 4.0)8.4High

Exploit odds (30 days)0.4%top 70.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 (as reported)

Vendor	Product	Versions
mwilliamson	mammoth.js	0 – before 1.12.2

Weakness: CWE-1321 · 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

References

https://raw.githubusercontent.com/mwilliamson/mammoth.js/master/NEWS release-notes, vendor-advisory
https://www.npmjs.com/package/mammoth product
https://github.com/mwilliamson/mammoth.js/commit/31f0c370be4b95ac4fa285fea3be970606735f16 patch
https://github.com/mwilliamson/mammoth.js/commit/2888fa158d67c1419199f152326e12a05618b53e patch