pypdf is an open source, pure-python PDF library. In affected versions an attacker may craft a PDF which leads to an infinite loop if parsecontentstream is executed. That is, for example, the case if the user extracted text from such a PDF. This issue was introduced in pull request #969 and resolved in pull request #1828. Users are advised to upgrade. Users unable to upgrade may modify the line while peek not in (b"\r", b"\n") in pypdf/generic/datastructures.py to while peek not in (b"\r", b"\n", b"").

Impact

An attacker who uses this vulnerability can craft a PDF which leads to an infinite loop if the PyPDF2 user wrote the following code:

python from PyPDF2 import PdfFileReader, PdfFileWriter from PyPDF2.pdf import ContentStream

reader = PdfFileReader("malicious.pdf", strict=False) for page in reader.pages: ContentStream(page.getContents(), reader)

Patches

PyPDF2==1.27.5 and later are patched.

Credits to Sebastian Krause for finding (issue) and fixing (PR) it.