Artifex MuPDF Denial-of-Service Vulnerability in `mutool clean` Utility

A denial-of-service vulnerability has been identified in Artifex MuPDF versions through 1.25.6. The issue arises in the `mutool clean` utility, where the `strip_outline()` function can enter an infinite recursion when processing a crafted PDF file with cyclic `/Next` references in the outline. This recursion continues until the program's stack is exhausted.

Impact

Exploitation of this vulnerability leads to an infinite recursion, causing the program to run out of stack space and potentially terminate unexpectedly.

Reproduction

The vulnerability can be reproduced by using the `mutool clean` command with a crafted PDF file that contains cyclic `/Next` references in the outline. This will trigger the infinite recursion in the `strip_outline()` function, exhausting the program's stack.

Remediation

Users can update to the latest version of MuPDF, where this vulnerability has been fixed. The patch is available in the official MuPDF repository.