CVE-2026-33123CWE-400CWE-407

pypdf has inefficient decoding of array-based streams

Medium · published March 20, 2026

CVSS v4.0
5.1
EPSS
0%
Percentile
31.8
In the wild
Unconfirmed
What it is

pypdf is a free and open-source pure-python PDF library. Versions prior to 6.9.1 allow an attacker to craft a malicious PDF which leads to long runtimes and/or large memory usage. Exploitation requires accessing an array-based stream with many entries. This issue has been fixed in version 6.9.1.

The record
Technical detail
CVSS v4.0
5.1 · MEDIUM
Vector
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
EPSS
0.00389 · 31.8th percentile
Weaknesses
CWE-400 · Uncontrolled Resource Consumption; CWE-407 · Inefficient Algorithmic Complexity
Published
2026-03-20T09:09Z
EPSS history
Timeline
  • 20 MAR 09:09Z
    pypdf has inefficient decoding of array-based streams
    cvelistv5