Out-of-bounds Read in Bigcat88 Pillow-Heif
CVE-2026-28231
pillow_heif is a Python library for working with HEIF images and plugin for Pillow. Prior to version 1.3.0, an integer overflow in the encode path buffer validation of `_pillow_heif.c` allows an attacker to bypass bounds checks by providing large image dimensions, resulting in a heap out-of-bounds read. This can lead to information disclosure (server heap memory leaking into encoded images) or denial of service (process crash). No special configuration is required — this triggers under default settings. Version 1.3.0 fixes the issue.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H.
EPSS exploit prediction
EPSS: 0.007 (51.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 52nd percentile — 51.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.007 · change: +0.001
Affected products
- Bigcat88 Pillow-Heif
- Bigcat88 Pillow Heif — versions < 1.3.0
Weakness classification (CWE)
References
- github.com/bigcat88/pillow_heif/security/advisories/GHSA-5gjj-6r7v-ph3x (Exploit, Mitigation, Vendor Advisory)
- github.com/bigcat88/pillow_heif/commit/8305a15d3780c533b762578cbe987d27a2c59c7a (Patch)
- github.com/bigcat88/pillow_heif/releases/tag/v1.3.0 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-28231?
- CVE-2026-28231 is a critical-severity vulnerability in Bigcat88 Pillow-Heif, classified under Out-of-bounds Read. CVSS score: 9.1/10. Published 2026-02-27.
- How severe is CVE-2026-28231?
- Critical severity. CVSS v3 base score is 9.1 out of 10.