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 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.
Vulnerability class: Buffer Overflow
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.002 (7.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 7th percentile — 7.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.001 · newest: 0.002 · change: +0.000
Affected products
- Python Pillow
- Python-Pillow Pillow — versions >= 11.2.1, < 12.2.0
Weakness classification (CWE)
References
- github.com/python-pillow/Pillow/security/advisories/GHSA-5xmw-vc9v-4wf2 (Vendor Advisory)
- github.com/python-pillow/Pillow/releases/tag/12.2.0 (Product, 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.