What’s Vulnerable › Vulnerabilities

CVE-2026-28231: pillow_heif Has Integer Overflow in Encode Path Buffer Validation that Leads to Heap Out-of-Bounds Read

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-02-27 · updated 2026-06-17
• Weakness: CWE-125

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 products

• bigcat88 pillow_heif: before 1.3.0 — fixed in 1.3.0

How to fix

Upgrade to a fixed version: bigcat88 pillow_heif 1.3.0. Check the vendor advisory for mitigations.

References

• https://github.com/bigcat88/pillow_heif/commit/8305a15d3780c533b762578cbe987d27a2c59c7a
• https://github.com/bigcat88/pillow_heif/releases/tag/v1.3.0
• https://github.com/bigcat88/pillow_heif/security/advisories/GHSA-5gjj-6r7v-ph3x

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