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 if the user extracted metadata from such a malformed PDF.

Patches The issue was fixed with https://github.com/py-pdf/pypdf/pull/1331

Workarounds If you cannot update your version of PyPDF2 (preferably to pypdf>3.1.0 as PyPDF2 is deprecated), you should modify PyPDF2/generic/datastructures.py::readobject.

Replace:

python else: # number object OR indirect reference peek = stream.read(20) stream.seek(-len(peek), 1) # reset to start if IndirectPattern.match(peek) is not None: return IndirectObject.readfromstream(stream, pdf) else: return NumberObject.readfromstream(stream)

by

python elif tok in b"0123456789+-.": # number object OR indirect reference peek = stream.read(20) stream.seek(-len(peek), 1) # reset to start if IndirectPattern.match(peek) is not None: return IndirectObject.readfromstream(stream, pdf) else: return NumberObject.readfromstream(stream) else: raise PdfReadError( f"Invalid Elementary Object starting with {tok} @{stream.tell()}" )

References pypdf issue #1329 pypdf PR #1331

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

Patches https://github.com/py-pdf/pypdf/pull/808

Workarounds Is there a way for users to fix or remediate the vulnerability without upgrading?

References PyPDF2 PR #808 PyPDF2 Issue #582

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"").