High severity · published Oct 29, 2026
CVE-2026-119205
pypdf: Possible infinite loop when cloning dictionaries
New
7.1
CVSS
–
EPSS
No
On KEV
Description
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.
Exploitation
Is it being used?
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PY
pypdf · py-pdf
< 6.21.4 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-119205
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-119205
x_refsource_CONFIRM
https://github.com/py-pdf/pypdf/security/advisories/GHSA-mfr5-77xh-9j7h
x_refsource_MISC
https://github.com/py-pdf/pypdf/pull/4288
x_refsource_MISC
https://github.com/py-pdf/pypdf/commit/f176db1a1f7f9af3e472e69a843ef1175653b044
x_refsource_MISC
https://github.com/py-pdf/pypdf/releases/tag/6.21.4
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