Intel

AIKIDO-2026-190935

mammoth is vulnerable to Uncontrolled Recursion

Uncontrolled Recursion Pre-CVE
Found by Aikido Intel before public disclosure or CVE publication.
Published Aug 12, 2026

53

Medium Risk

This Affects:

PYTHONmammoth
1.4.9 - 1.12.0
Fixed in 1.12.1
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TL;DR

The numbering parser resolves a numbering definition's numStyleLink by following it to another numbering style and recursing into that style. A crafted document whose numbering styles reference one another, or a style that references itself, makes this resolution recurse without ever terminating. Converting such a document exhausts the call stack and aborts the conversion, denying service for that input. The fix records already-visited numbering IDs and stops when a cycle is detected.

Who does this affect?

You are affected if you are using a version that falls within the vulnerable range and your application converts untrusted .docx documents, via either the library convert API or the command-line interface.

Background info

mammoth is vulnerable to Uncontrolled Recursion in versions 1.4.9 - 1.12.0.

How to fix this

Upgrade the mammoth library to the patch version.