CVE-2026-41313: pypdf: Possible long runtimes for wrong size values in incremental mode

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-22 · updated 2026-06-17
Weakness: CWE-834

Description

pypdf is a free and open-source pure-python PDF library. An attacker who uses a vulnerability present in versions prior to 6.10.2 can craft a PDF which leads to long runtimes. This requires loading a PDF with a large trailer `/Size` value in incremental mode. This has been fixed in pypdf 6.10.2. As a workaround, one may apply the changes from the patch manually.

Affected products

py-pdf pypdf: before 6.10.2 — fixed in 6.10.2

How to fix

Upgrade to a fixed version: py-pdf pypdf 6.10.2. Check the vendor advisory for mitigations.

References

https://github.com/py-pdf/pypdf/commit/c50a0104cf083356f7c7f5d61410466a57f5c88a
https://github.com/py-pdf/pypdf/pull/3735
https://github.com/py-pdf/pypdf/releases/tag/6.10.2
https://github.com/py-pdf/pypdf/security/advisories/GHSA-4pxv-j86v-mhcw

Get alerted when CVE-2026-41313 or the next vulnerability affects your stack