What’s Vulnerable › Vulnerabilities

CVE-2021-25292: Regular Expression Denial of Service (ReDoS) in Pillow

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.7% 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-1333

Description

An issue was discovered in Pillow before 8.1.1. The PDF parser allows a regular expression DoS (ReDoS) attack via a crafted PDF file because of a catastrophic backtracking regex.

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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