CVE-2026-119204: pypdf: Possible large memory usage when parsing page tree

Severity: high (CVSS 7.1 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-29 · updated 2026-10-30
Weakness: CWE-400

Description

pypdf is a free and open-source pure-python PDF library. Prior to 6.21.4, pypdf can consume excessive memory while parsing a crafted PDF page tree containing many shared resources. Page-tree flattening copies page dictionary and inherited resource entries without a document-wide entry budget, allowing the crafted resource structure to cause disproportionate allocations. This issue is fixed in version 6.21.4.

Affected products

py-pdf pypdf: before 6.21.4

References

https://github.com/py-pdf/pypdf/commit/ea4ac663133f1b3de1d7a8f2e6fa239802fde79e
https://github.com/py-pdf/pypdf/pull/4290
https://github.com/py-pdf/pypdf/releases/tag/6.21.4
https://github.com/py-pdf/pypdf/security/advisories/GHSA-cggf-277g-3q54

Get alerted when CVE-2026-119204 or the next vulnerability affects your stack