GHSA-MRFP-P49P-3HF2 Pillow PDF append accepts malformed shared page-tree DAG causing resource exhaustion

Summary Pillow's documented PDF append path can spend disproportionate CPU time on a compact malformed PDF page tree. An attacker who can supply an existing PDF to an application that appends an image with Image.save..., format="PDF", append=True can provide a malformed /Pages tree where each lev...

CVE-2026-96640 Pillow PDF append accepts malformed shared page-tree DAG causing resource exhaustion

Pillow is a Python imaging library. From 5.1.0 until 13.0.0, PdfParser.linearizepagetree 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...

CVE-2026-96640 Pillow PDF append accepts malformed shared page-tree DAG causing resource exhaustion

Pillow is a Python imaging library. From 5.1.0 until 13.0.0, PdfParser.linearizepagetree 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...

CVE-2026-96640

The Pillow Python imaging library versions 5.1.0 through 13.0.0 are vulnerable to a resource exhaustion issue in the PdfParser.linearize_page_tree() function located in src/PIL/PdfParser.py . The root cause is that the parser treats a PDF /Pages graph as a tree without tracking duplicate indirect...