CVE-2026-84311: pypdf is a free and open-source pure-python PDF library. Prior to 6.16.1, an attacker can craft a PDF that causes pypdf/_page.py PageObject.

CVE-2026-84311 · Severity: medium · CVSS 4 · Published 2026-09-01

pypdf is a Python library used to extract, manipulate, and analyze PDF files. A vulnerability in how pypdf processes XForm objects (a PDF feature for reusable content) allows an attacker to craft a malicious PDF that consumes excessive memory and processing time when text is extracted. This can cause applications using pypdf to become unresponsive or crash, disrupting any service that relies on automated PDF processing.

Technologies: pypdf (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-84311 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-84311 being exploited in the wild.
How severe is CVE-2026-84311?
Medium severity, with a CVSS score of 4, published 1 September 2026.
Which products and versions are affected?
pypdf (PyPI) < 6.16.1, ECOSYSTEM:introduced=0,fixed=6.16.1.
Is there a fix for CVE-2026-84311?
Yes. pypdf (PyPI): upgrade to 6.16.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-84311 attacked?
It is attacked with local access, in a software library.
Am I affected by CVE-2026-84311?
Check whether you run pypdf (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • pypdf (PyPI): upgrade to 6.16.1 or later
    pip install "pypdf>=6.16.1"

Technical details

The vulnerability is rooted in excessive iteration (CWE-834) during XForm object extraction, specifically when handling reused XForm objects within a PDF. The vulnerable code path is triggered when an application calls text extraction on a page containing multiple or reused XForm objects. An attacker can craft a PDF with specially designed XForm structures that cause the parser to iterate far beyond necessary bounds, leading to polynomial or exponential runtime and memory exhaustion. The attack vector is local with passive user interaction (the victim must attempt to extract text from the malicious PDF). No authentication or elevated privileges are required. The fix is available in pypdf 6.16.1; users unable to upgrade may apply the patch from PR #3966.

Affected products

  • py-pdf pypdf < 6.16.1

Identifiers

  • CVE-2026-84311
  • GHSA-763m-79hh-57f2
  • PYSEC-2026-3911

Timeline

  • 2026-08-14: disclosed: GitHub Advisory published
  • 2026-09-01: patched: Fix released in pypdf 6.16.1
  • 2026-09-01: advisory: Public advisory updated

References

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