CVE-2025-66019 MEDIUM

CVE-2025-66019: pypdf manipulated LZWDecode streams can exhaust RAM

Vendor Py-Pdf
Product pypdf
Weakness CWE-400
Published November 25, 2025
Last update January 20, 2026
View on NVD All CVEs

CVSS base score

6.6/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality —
Integrity —

CVSS vector

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

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

November 25, 2025 CVE published
January 20, 2026 Record updated