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

> Attackers can cause a denial of service in applications using Mammoth.js by supplying a crafted .docx file that triggers a regular expression denial of service.

- **Severity:** High 8.7 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Oct 2026
- **Updated:** 5 Oct 2026
- **Also known as:** GHSA-fp33-4hh4-xjj5

## What is CVE-2026-105219?

CVE-2026-105219 is a high-severity denial of service vulnerability in mwilliamson mammoth.js, published on 4 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-1333 (Inefficient Regular Expression Complexity)

## Which versions are affected by CVE-2026-105219?


## How do I fix CVE-2026-105219?

No fix has been published for CVE-2026-105219 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-105219 being exploited?

There is no known exploitation of CVE-2026-105219 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-105219 and fix it if it is affected.

What it is: CVE-2026-105219 is a high-severity denial of service vulnerability in mwilliamson mammoth.js, published on 4 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-105219 in the wild and no public exploit code.

Affected product: mwilliamson mammoth.js. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-105219/ (Markdown: https://insights.sbomify.com/CVE-2026-105219/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-105219
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-105219
- OSV: https://osv.dev/vulnerability/CVE-2026-105219

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-105219/
Summaries are generated and may contain mistakes; the official description above is the record.