CVE-2025-66019

pypdf manipulated LZWDecode streams can exhaust RAM

State: Published
Severity: 6.6 Medium
Published: Nov 25, 2025
Updated: Jan 20, 2026
Reserved: Nov 21, 2025

Description

pypdf is a free and open-source pure-python PDF library. Prior to version 6.4.0, an attacker who uses this vulnerability can craft a PDF which leads to a memory usage of up to 1 GB per stream. This requires parsing the content stream of a page using the LZWDecode filter. This issue has been patched in version 6.4.0.

Scores

CVSS	Score	Vector	Source
4.0	6.6 Medium	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U	GitHub_M

Weaknesses

CWE-400 Uncontrolled Resource Consumption
CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)

Affected Products

Product	Versions
pypdfpy-pdf	< 6.4.0Affected

References

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