high7.5
CVE-2026-96640
Pillow PDF append accepts malformed shared page-tree DAG causing resource exhaustion
Impact
Pillow is a Python imaging library. From 5.1.0 until 13.0.0, PdfParser.linearize_page_tree() in src/PIL/PdfParser.py treats a PDF /Pages graph as a tree without tracking duplicate indirect references. When Image.save(..., format="PDF", append=True) processes an attacker-controlled existing PDF whose /Kids arrays repeatedly reference the same child /Pages node, Pillow expands the shared subtree as distinct pages. A compact malformed PDF can therefore create exponentially many page references and consume disproportionate CPU before the append completes. This issue is fixed in version 13.0.0.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | Pillow | >= 5.1.0, < 13.0.0 | 13.0.0 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Python | Pillow | from 5.1.0 before 13.0.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-mrfp-p49p-3hf2
- https://github.com/python-pillow/Pillow/security/advisories/GHSA-mrfp-p49p-3hf2
- https://nvd.nist.gov/vuln/detail/CVE-2026-96640
- https://github.com/python-pillow/Pillow/pull/10093
- https://github.com/python-pillow/Pillow/commit/6f0e7ee1f9c2fe227906f8a4b926e6622b702bc7
- https://github.com/python-pillow/Pillow/releases/tag/13.0.0