Description
pypdf is a free and open-source pure-python PDF library. An attacker who uses a vulnerability present in versions 3.7.0 through 3.16.4 can craft a PDF which leads to an infinite loop. This infinite loop blocks the current process and can utilize a single core of the CPU by 100%. It does not affect memory usage. That is, for example, the case when the pypdf-user manipulates an incoming malicious PDF e.g. by merging it with another PDF or by adding annotations. The issue was fixed in version 3.17.0. As a workaround, apply the patch manually by modifying `pypdf/generic/_data_structures.py`.
Affected products
py-pdf: pypdf
References6
- github.com/py-pdf/pypdf/security/advisories/GHSA-wjcc-cq79-p63f Vendor Advisory
- github.com/py-pdf/pypdf/security/advisories/GHSA-wjcc-cq79-p63f Vendor Advisory
- github.com/py-pdf/pypdf/commit/9b23ac3c9619492570011d551d521690… Patch
- github.com/py-pdf/pypdf/pull/2264 Issue TrackingPatch
- github.com/py-pdf/pypdf/commit/9b23ac3c9619492570011d551d521690… Patch
- github.com/py-pdf/pypdf/pull/2264 Issue TrackingPatch
Metrics
- CVSS 3.1
-
5.5
MEDIUM
Score source: NVD
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - EPSS — exploit probability
- 0% percentile: 17 · as of 5 November 2026
- CWE
- CWE-835
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.