Vulnerability · Published Feb 27, 2026 · Assigned by GitHub_M
CVE-2026-28231pillow_heif Has Integer Overflow in Encode Path Buffer Validation that Leads to Heap Out-of-Bounds Read
Medium 5.5
In plain English
A medium-severity out-of-bounds read in pillow_heif from bigcat88. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 53% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | pi-heif | 1.3.0 | GHSA-5gjj-6r7v-ph3x |
| PyPI | pi-heif | 1.3.0 | PYSEC-2026-2248 |
| PyPI | pillow-heif | 1.3.0 | GHSA-5gjj-6r7v-ph3x |
| PyPI | pillow-heif | 1.3.0 | PYSEC-2026-2258 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| bigcat88 | pillow_heif | < 1.3.0 |
Weakness: CWE-125, CWE-190 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P