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CVE-2026-96638— Pillow: BMP RLE decoder memory-amplification DoS via unbounded delta escape / absolute mode

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 9.1.0 至 13.0.0 版本中， 文件里的 方法允许精心构造的 RLE BMP 增量（delta）转义序列和绝对模式运行（runs）在超出剩余目标长度（dest_length）的情况下继续追加数据，且缺乏针对各分支的容量限制。由于一个增量操作可在单次迭代中添加约 255 行图像数据，因此一个仅几千字节大小但宽度较大的文件，可将其数据字节数组（bytearray）扩展至数百兆字节甚至更多，从而引发内存耗尽型拒绝服务（DoS）攻击。该问题已在 13.0.0 版本

CVSS 6.5 · Medium

Possible ATT&CK Techniques 1 AI

T1499.003 · Application Exhaustion Flood
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I. Basic Information for CVE-2026-96638

Vulnerability Information
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Vulnerability Title
Pillow: BMP RLE decoder memory-amplification DoS via unbounded delta escape / absolute mode
Source: CVE Program / CVE List V5
Vulnerability Description
Pillow is a Python imaging library. From 9.1.0 until 13.0.0, BmpRleDecoder.decode() in src/PIL/BmpImagePlugin.py permits crafted RLE BMP delta escapes and absolute-mode runs to append beyond the remaining dest_length without a per-branch cap. A delta can add roughly 255 image rows in one iteration, so a kilobyte-sized file with a large but permitted width can expand the data bytearray to hundreds of megabytes or more, causing memory-exhaustion denial of service. This issue is fixed in version 13.0.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
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 >= 9.1.0, < 13.0.0 -

II. Public POCs for CVE-2026-96638

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III. Intelligence Information for CVE-2026-96638

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Patches & Fixes for CVE-2026-96638 (2)

Vendor Advisories for CVE-2026-96638 (1)

Vendor Pages for CVE-2026-96638 (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-2026-96640 8.2 HIGH Pillow PDF append accepts malformed shared page-tree DAG causing resource exhaustion
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-2026-96641 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-2026-96638

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