Prototype pollution in mwilliamson mammoth.js
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- —
- Confidentiality · integrity · availability
- High · Low · High
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| mwilliamson | mammoth.js | before 1.12.2 | 1.12.2 | Patch available | CNA |
- mammoth.js Vendormwilliamson Affected before 1.12.2 Fixed in 1.12.2 Patch available CNA
Remediation
- Fix · CNA mammoth.js (mwilliamson) Fixed in 1.12.2
Timeline
- 2026-10-02 Threatist record created from CVE-2026-97151
- 2026-10-03 Alias added: GHSA-89qm-22qm-xf5h
References
Patch 2
More mwilliamson vulnerabilities
- TI-2026-67557 Mammoth.js 1.3.0 before 1.12.3 ReDoS via Style Map Tokeniser CVSS 4.0HIGH 8.7
Sources
- CVE-2026-97151 · CVE Program
- CVE-2026-97151 · NVD
- FIRST EPSS
- GHSA-89qm-22qm-xf5h · GitHub Advisory Database · CC BY 4.0
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