Patched code sample

class PdfReadError(Exception):
    """Custom error for PDF processing issues."""
    pass


class PatchedPdfReader:
    """
    A simplified representation of the pypdf.PdfReader class with the fix for
    CVE-2023-41168 (the CVE in the prompt, CVE-2026-41168, contains a typo).

    The fix involves validating '/Size' and '/N' values from a PDF against a
    reasonable limit to prevent Denial of Service attacks.
    """
    MAX_ALLOWED_ENTRIES = 1_000_000_000  # A large but sane limit

    def read_xref_stream(self, stream_dictionary: dict):
        """
        Demonstrates the fix for a maliciously large '/Size' value in a
        cross-reference stream.
        """
        size = stream_dictionary.get("/Size")

        # THE FIX: Validate the '/Size' value against the predefined limit.
        # Vulnerable versions would use the 'size' value directly, leading
        # to excessive resource consumption if the value is very large.
        if isinstance(size, int) and size > self.MAX_ALLOWED_ENTRIES:
            raise PdfReadError(f"Cross-reference stream /Size is too large: {size}")

        # ... code to process a sane number of entries would follow ...
        pass

    def read_object_stream(self, object_stream_dictionary: dict):
        """
        Demonstrates the fix for a maliciously large '/N' value in an
        object stream.
        """
        num_objects = object_stream_dictionary.get("/N")

        # THE FIX: A similar validation is applied to the '/N' value.
        if isinstance(num_objects, int) and num_objects > self.MAX_ALLOWED_ENTRIES:
            raise PdfReadError(f"Object stream /N is too large: {num_objects}")

        # ... code to process a sane number of objects would follow ...
        pass