mammoth (aka mammoth.js) before 1.12.2 is vulnerable to prototype pollution when reading the styles defined in a document
Published Sep 24, 2026
8.4
HIGHCVSS 4.0
EPSS 0.36%
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
-
- Version 0StatusaffectedConstraints<1.12.2
- Version
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Mwilliamson | Mammoth.js | unaffected |
|
No data.
No data.
No Red Hat product state for this CVE.
No package ranges for this CVE.
Remediation
Vendor solution
Upgrade to mammoth 1.12.2 or later.
Metrics
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
No CVSS v3.1 score for this CVE.
No CVSS v3.0 score for this CVE.
No CVSS v2.0 score for this CVE.
This CVE is not in the KEV list.
CISA SSVC (Vulnrichment)
Stakeholder-Specific Vulnerability Categorization from CISA ADP.
Exploitation
NoneAutomatable
NoTechnical Impact
PartialDecision
n/aAssessed Sep 24, 2026 · SSVC 2.0.3
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 3, 2026.
Score over time
Oct 2026- EPSS v5
Percentile over time
- EPSS v5
Table of values (2 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 3, 2026 | 0.36% (0.00355) | 27.00th | v5 (v2026.06.15) |
| Oct 1, 2026 | 0.36% (0.00355) | 26.92th | v5 (v2026.06.15) |
References (4)
- https://github.com/mwilliamson/mammoth.js/commit/2888fa158d67c1419199f152326e12a05618b53e patch
- https://github.com/mwilliamson/mammoth.js/commit/31f0c370be4b95ac4fa285fea3be970606735f16 patch
- https://raw.githubusercontent.com/mwilliamson/mammoth.js/master/NEWS release-notesvendor-advisory
- https://www.npmjs.com/package/mammoth product
Change history (0)
No recorded changes yet.