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CVE-2026-22690 — pypdf has possible long runtimes for missing /Root object with large /Size values

2026-09-29T03:49:21.197701+00:00

Affected: py-pdf pypdf

pypdf is a free and open-source pure-python PDF library. Prior to version 6.6.0, pypdf has possible long runtimes for missing /Root object with large /Size values. An attacker who uses this vulnerability can craft a PDF which leads to possibly long runtimes for actually invalid files. This can be achieved by omitting the /Root entry in the trailer, while using a rather large /Size value. Only the non-strict reading mode is affected. This issue has been patched in version 6.6.0.

GHSA-4xc4-762w-m6cg — pypdf has possible long runtimes for missing /Root object with large /Size values

2026-09-29T03:49:21.197793+00:00

Affected: PyPI: pypdf

### Impact An attacker who exploits this vulnerability can craft a PDF which leads to possibly long runtimes for actually invalid files. This can be achieved by omitting the `/Root` entry in the trailer, while using a rather large `/Size` value. Only the non-strict reading mode is affected.

### Patches This has been fixed in [pypdf==6.6.0](https://github.com/py-pdf/pypdf/releases/tag/6.6.0).

### Workarounds

```python from pypdf import PdfReader, PdfWriter

# Instead of reader = PdfReader("file.pdf") # use the strict mode: reader = PdfReader("file.pdf", strict=True)

# Instead of writer = PdfWriter(clone_from="file.pdf") # use an explicit strict reader: writer = PdfWriter(clone_from=PdfReader("file.pdf", strict=True)) ```

### Resources This issue has been fixed in #3594.

PYSEC-2026-1829 — pypdf has possible long runtimes for missing /Root object with large /Size values