Description
pypdf is a free and open-source pure-python PDF library. Prior to 6.20.0, an attacker can craft an incomplete PDF that ends inside a standard cross-reference table, causing pypdf to mishandle the unexpected end of file and enter an infinite loop. This issue is fixed in version 6.20.0.
Affected products
py-pdf: pypdf
References5
- github.com/py-pdf/pypdf/security/advisories/GHSA-39mj-jf6j-2qj3 Vendor Advisory
- github.com/py-pdf/pypdf/commit/37e1cd681744bac38b159f7e1c614eee… Patch
- github.com/py-pdf/pypdf/issues/4169 Issue TrackingPatch
- github.com/py-pdf/pypdf/pull/4170 Issue TrackingPatch
- github.com/py-pdf/pypdf/releases/tag/6.20.0 Release Notes
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 - CVSS 4.0
-
6.0
MEDIUM
Score source: CNA
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 29 · as of 8 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.