CVE-2026-42309: python-pillow pillow Heap-based Buffer Overflow

Vulnerability summary

CVE-2026-42309 is a medium (CVSS 5.5) Heap-based Buffer Overflow vulnerability in python-pillow pillow. EPSS estimates a 0.18% chance of exploitation in the next 30 days, higher than 7.2% of scored vulnerabilities.

Timeline

1. 09-05-2026
   PublishedVulnerability first disclosed.
2. 11-05-2026
   Last modifiedVulnerability information updated.

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.

• CWE-122Heap-based Buffer OverflowA 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().