forked from pool/python-PyPDF2
42 lines
1.7 KiB
Diff
42 lines
1.7 KiB
Diff
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From 0fbd95938724ad2d72688d4112207c0590f0483f Mon Sep 17 00:00:00 2001
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From: rampageservices <20424586+rampageservices@users.noreply.github.com>
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Date: Sat, 21 Feb 2026 23:17:20 +0800
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Subject: [PATCH] BUG: Prevent infinite loop from circular xref /Prev
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references
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Malformed PDFs can contain circular /Prev references in the xref
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chain (e.g., xref A -> /Prev -> xref B -> /Prev -> xref A).
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This causes _read_xref_tables_and_trailers() to loop forever,
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spamming "Overwriting cache for N M" warnings on every iteration
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as the same objects are re-parsed and re-cached indefinitely.
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Fix: Track visited xref offsets in a set. If a startxref value
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has already been visited, log a warning and break the loop.
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Closes #3654
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---
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PyPDF2/_reader.py | 9 +++++++++
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1 file changed, 9 insertions(+)
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Index: PyPDF2-2.11.1/PyPDF2/_reader.py
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===================================================================
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--- PyPDF2-2.11.1.orig/PyPDF2/_reader.py
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+++ PyPDF2-2.11.1/PyPDF2/_reader.py
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@@ -1564,7 +1564,16 @@ class PdfReader:
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self.xref_free_entry: Dict[int, Dict[Any, Any]] = {}
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self.xref_objStm: Dict[int, Tuple[Any, Any]] = {}
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self.trailer = DictionaryObject()
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+ visited_xref_offsets: set[int] = set()
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while startxref is not None:
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+ # Detect circular /Prev references in the xref chain
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+ if startxref in visited_xref_offsets:
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+ logger_warning(
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+ f"Circular xref chain detected at offset {startxref}, stopping",
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+ __name__,
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+ )
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+ break
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+ visited_xref_offsets.add(startxref)
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# load the xref table
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stream.seek(startxref, 0)
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x = stream.read(1)
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