CVE-2021-25289: Out of bounds write in Pillow

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-03-19 · updated 2026-06-17
Weakness: CWE-787

Description

An issue was discovered in Pillow before 8.1.1. TiffDecode has a heap-based buffer overflow when decoding crafted YCbCr files because of certain interpretation conflicts with LibTIFF in RGBA mode. NOTE: this issue exists because of an incomplete fix for CVE-2020-35654.

Affected products

python-pillow Pillow: before 8.1.1 — fixed in 8.1.1
Pypi Pillow: before 8.1.1; 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 (+71) — fixed in 8.1.1

How to fix

Upgrade to a fixed version: python-pillow Pillow 8.1.1; Pypi Pillow 8.1.1. Check the vendor advisory for mitigations.

References

https://pillow.readthedocs.io/en/stable/releasenotes/8.1.1.html
https://security.gentoo.org/glsa/202107-33
https://pillow.readthedocs.io/en/stable/releasenotes/8.1.1.html
https://security.gentoo.org/glsa/202107-33

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