Possible Infinite Loop when PdfWriter(clone_from) is used with a PDF

Impact

An attacker who uses this vulnerability can craft a PDF which leads to an infinite loop.
This infinite loop blocks the current process and can utilize a single core of the CPU by 100%. It does not affect memory usage.

That is, for example, the case when the pypdf-user manipulates an incoming malicious PDF e.g. by merging it with another PDF or by adding annotations.

Patches

The issue was fixed with #2264

Workarounds

If you cannot update your version of pypdf, you should modify pypdf/generic/_data_structures.py just like #2264 did.