What is CVE-2026-42309?

CVE-2026-42309 is a medium-severity vulnerability in Python Pillow, classified under Heap-based Buffer Overflow. CVSS score: 5.5/10. Published 2026-05-09.

How severe is CVE-2026-42309?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Buffer overflow in Python Pillow

CVE-2026-42309

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 ca…

Vulnerability class: Buffer Overflow

EPSS: 0.000 (3.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

Affected products

Python Pillow
Python-pillow Pillow — versions >= 11.2.1, < 12.2.0

Weakness classification (CWE)

CWE-122 — Heap-based Buffer Overflow

References

security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
security-advisories@github.com (Product, x_refsource_MISC, Release Notes)

Frequently asked questions

What is CVE-2026-42309?: CVE-2026-42309 is a medium-severity vulnerability in Python Pillow, classified under Heap-based Buffer Overflow. CVSS score: 5.5/10. Published 2026-05-09.
How severe is CVE-2026-42309?: Medium severity. CVSS v3 base score is 5.5 out of 10.