pypdf is a free and open-source pure-python PDF library. Prior to version 6.0.0, an attacker can craft a PDF which leads to the RAM being exhausted. This requires just reading the file if a series of FlateDecode filters is used on a malicious cross-reference stream. Other content streams are affected on explicit access. This issue has been fixed in 6.0.0. If an update is not possible, a workaround involves including the fixed code from pypdf.filters.decompress into the existing filters file.
CVE-2025-55197
CVSS base score
7.5 (v3.1)
Severity
HIGH
Attack vector
Network
Weakness
CWE-400, CWE-770
Last modified
November 2, 2026
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected products
py-pdf pypdf
References
- github.com Product
- github.com Issue Tracking
- github.com Patch
- github.com Release Notes
- github.com Mitigation, Third Party Advisory