CVE-2026-42309
Received Received - Intake
Heap Buffer Overflow in Pillow Image Processing Library

Publication date: 2026-05-09

Last updated on: 2026-05-09

Assigner: GitHub, Inc.

Description
Pillow is a Python imaging library. From version 11.2.1 to before version 12.2.0, passing nested lists as coordinates to APIs that accept coordinates such as ImagePath.Path, ImageDraw.ImageDraw.polygon and ImageDraw.ImageDraw.line could cause a heap buffer overflow, as nested lists were recursively unpacked beyond the allocated buffer. Coordinate lists are now validated to contain exactly two numeric coordinates. This issue has been patched in version 12.2.0.
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Meta Information
Published
2026-05-09
Last Modified
2026-05-09
Generated
2026-06-19
AI Q&A
2026-05-09
EPSS Evaluated
2026-06-18
NVD
CVE-2026-42309
EUVD
EUVD-2026-28901
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
python pillow From 11.2.1 (inc) to 12.2.0 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-122 A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
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Executive Summary

CVE-2026-42309 is a heap buffer overflow vulnerability in the Python Pillow imaging library affecting versions 11.2.1 to before 12.2.0.

The issue occurs when nested lists are passed as coordinates to certain Pillow APIs such as ImagePath.Path, ImageDraw.ImageDraw.polygon, and ImageDraw.ImageDraw.line. These nested lists were recursively unpacked beyond the allocated buffer size, causing a heap buffer overflow.

This vulnerability was introduced in version 11.2.1 and has been fixed in version 12.2.0 by validating that coordinate lists contain exactly two numeric coordinates.

Impact Analysis

This heap buffer overflow vulnerability can lead to memory corruption when processing images with Pillow using the affected functions.

Memory corruption issues like this can cause application crashes, unexpected behavior, or potentially allow an attacker to execute arbitrary code or escalate privileges depending on the context in which Pillow is used.

Since Pillow is widely used for image processing in Python applications, exploiting this vulnerability could compromise the stability and security of applications that process untrusted image data.

Mitigation Strategies

To mitigate this vulnerability, upgrade the Python Pillow library to version 12.2.0 or later.

This version includes a patch that validates coordinate lists to contain exactly two numeric coordinates, preventing the heap buffer overflow caused by nested lists.

Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

Detection Guidance

This vulnerability affects Python Pillow library versions from 11.2.1 up to 12.1.0. To detect if your system is vulnerable, you should check the installed Pillow version.

You can run the following Python command to check the Pillow version installed on your system:

  • python -c "import PIL; print(PIL.__version__)"

If the version is between 11.2.1 and before 12.2.0, your system is vulnerable to this heap buffer overflow issue.

There are no specific network detection commands or signatures mentioned for this vulnerability, as it is a local library issue triggered by passing nested lists as coordinates in certain Pillow API calls.

To mitigate or confirm the fix, upgrade Pillow to version 12.2.0 or later, where the vulnerability has been patched.

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