mupdf fails to open a PDF file with UserUnit definition (very large page size)

[Manuel Geißer]

Summary
The mupdf PDF viewer fails to open a certain file created by Adobe Illustrator.
The file can be downloaded at "https://github.com/cfcurtis/pdfstitcher/raw/a1a2707af93bb580745e58776c53d6545aea5749/test/userunit_10.pdf" and is also attached.
The file has a very large page size due to a /UserUnit definition of 10.

Observed Result
When attempting to open the file with mupdf, it takes a long time, and finally terminates with a segmentation fault. The file is valid and opens with Adobe Reader.

Expected Result
The file should open and render correctly with mupdf, without a segmentation fault and at reasonable speed.

OS: Ubuntu Focal 20.04
MuPDF version: 1.16.1

[Manuel Geißer (geisserml)]

Please note that most open-source PDF applications, like Okular, Chromium, Firefox, Inkscape, Scribus, and PDF Arranger do not properly recognise the page size of this file and display it smaller than intended, because they do not take the UserUnit property into account.
For more details, see https://bugs.kde.org/show_bug.cgi?id=442280

[Manuel Geißer (geisserml)]

Interestingly PyMuPDF 1.18.17 (installed via pip) can render the page correctly.