Pillow has a heap buffer overflow with nested list coordinates — CVE-2026-42309

Summary

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 was introduced in Pillow 11.2.1.

Product

pip: pillow

What to do

General, cautious steps (verify details in the official source):

• Review exposure and plan remediation based on risk and environment.
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

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