pypdf is a free and open-source pure-python PDF library. Prior to 6.21.4, pypdf can enter an infinite loop when cloning or duplicating a crafted cyclic DictionaryObject. Clone traversal checked generated destination references rather than the original source references, allowing some source cycles to evade the visited-object check. This issue is fixed in version 6.21.4.
CVE-2026-119205
CVSS base score
5.5 (v3.1)
Severity
MEDIUM
Attack vector
Local
Weakness
CWE-835
Last modified
November 2, 2026
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Affected products
py-pdf pypdf
References
- github.com Patch
- github.com Patch
- github.com Release Notes
- github.com Patch, Vendor Advisory