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

Quick assessment

Affected
python-pillow Pillow
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Pillow 是一个 Python 图像处理库。在 5.1.0 至 13.0.0 版本中， 文件里的 方法将 PDF 的 图结构视为树结构，但未追踪重复的间接引用。当调用 处理由攻击者控制的现有 PDF 时，若该 PDF 的 数组反复引用同一个子 节点，Pillow 会将共享的子树展开为多个独立的页面。因此，一个紧凑的畸形 PDF 可生成指数级增长的页面引用，在追加操作完成前消耗不成比例的 CPU 资源。该问题已在 13.0.0 版本中修复。

CVSS 8.2 · High
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I. Basic Information for CVE-2026-96640

Vulnerability Information
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Vulnerability Title
Pillow PDF append accepts malformed shared page-tree DAG causing resource exhaustion
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
python-pillow Pillow >= 5.1.0, < 13.0.0 -

II. Public POCs for CVE-2026-96640

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III. Intelligence Information for CVE-2026-96640

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Patches & Fixes for CVE-2026-96640 (2)

Vendor Advisories for CVE-2026-96640 (1)

Vendor Pages for CVE-2026-96640 (1)

Same Patch Batch · python-pillow · 2026-10-21 · 11 CVEs total

CVE-2026-96639 9.8 CRITICAL Pillow multi-frame loaders can reuse stale native image storage after mode transitions
CVE-2026-96778 7.7 HIGH Pillow: Heap buffer overflow writing JPEG comment after ICC profile fills buffer
CVE-2026-96642 7.1 HIGH Pillow: TarIO negative size field causes infinite CPU-spin loop
CVE-2026-96643 7.1 HIGH Pillow: PNG eXIf chunk makes EXIF parsing run in quadratic time
CVE-2026-96644 7.1 HIGH Pillow: Heap over-read in WMF/EMF rendering via 16-bit dimension truncation (Windows build
CVE-2026-96637 7.1 HIGH Pillow: Decompression bomb check bypass in SpiderImagePlugin.seek() leads to unbounded all
CVE-2026-96638 6.5 MEDIUM Pillow: BMP RLE decoder memory-amplification DoS via unbounded delta escape / absolute mod
CVE-2026-96641 6.5 MEDIUM Pillow: Reachable undefined behavior in native integer operations, potentially leading to
CVE-2026-96636 6.5 MEDIUM Pillow: Decompression-bomb protection bypass via multi-frame seek() in MPO and DCX (MpoIma
CVE-2026-114501 6.3 MEDIUM Pillow: Arrow export leaks stale heap memory when PILLOW_ALIGNMENT > 1

IV. Related Vulnerabilities

Same product: Pillow
Same vendor: python-pillow
Same weakness: CWE-400

V. Comments for CVE-2026-96640

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