Improper Handling of Highly Compressed Data (Data Amplification) Affecting pypdf package, versions [,6.4.0)
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Test your applications- Snyk IDSNYK-PYTHON-PYPDF-14105065
- published25 Nov 2025
- disclosed24 Nov 2025
- creditYunus AYDIN
Introduced: 24 Nov 2025
NewCVE-2025-66019 (opens in a new tab)Common Vulnerabilities and Exposures (CVE) are common identifiers for publicly known security vulnerabilities
Common Weakness Enumeration (CWE) is a category system for software weaknesses
How to fix?
Upgrade pypdf to version 6.4.0 or higher.
Overview
pypdf is an A pure-python PDF library capable of splitting, merging, cropping, and transforming PDF files
Affected versions of this package are vulnerable to Improper Handling of Highly Compressed Data (Data Amplification) via the LZWDecode process. An attacker can exhaust system memory by crafting a PDF that triggers excessive memory allocation during content stream parsing. This is only exploitable if the content stream of a page uses the LZWDecode filter.
Workaround
This vulnerability can be mitigated by setting pypdf.filters.LZW_MAX_OUTPUT_LENGTH = 75_000_000.