# CVE-2026-113789: pypdf denial of service via malicious form fields

Source: https://junglewise.ai/threats/cve-2026-113789-pypdf-is-a-free-and-open-source-pure-python-pdf-library-prior-to  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-21. Updated: 2026-10-21  
License: CC BY 4.0 with a link back

CVE-2026-113789 · Severity: medium · CVSS 4 · Published 2026-10-21

pypdf is a Python library for reading and manipulating PDF files. An attacker can craft a malicious PDF with deeply nested or numerous form fields that causes applications using pypdf to consume excessive memory or take very long to process when retrieving the document's form fields, resulting in a denial of service.

Technologies: [Py-Pdf Pypdf](https://junglewise.ai/threats/technologies/py-pdf-pypdf), [pypdf (PyPI)](https://junglewise.ai/threats/technologies/pypdf). Vendors: [Py-Pdf](https://junglewise.ai/threats/vendors/py-pdf), [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-113789 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-113789 being exploited in the wild.

**How severe is CVE-2026-113789?** Medium severity, with a CVSS score of 4, published 21 October 2026.

**Which products and versions are affected?** Py-Pdf Pypdf prior to 6.21.0; pypdf (PyPI) < 6.21.0, ECOSYSTEM:introduced=0,fixed=6.21.0.

**Is there a fix for CVE-2026-113789?** Yes. pypdf (PyPI): upgrade to 6.21.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-113789 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-113789?** Check whether you run Py-Pdf Pypdf or 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 6.21.0 or later

  ```sh
  pip install "pypdf>=6.21.0"
  ```


## Technical details

The vulnerability exists in the form field retrieval functionality of pypdf prior to 6.21.0, where insufficient limits on field nesting depth and field count allow algorithmic complexity attacks. The get_fields method lacks proper boundaries, permitting an attacker to craft a PDF with circular references or exponential nesting that exhausts system resources. The fix introduces maximum limits on form field count (100,000 entries) and nesting depth (100 levels).

## Affected products

- py-pdf pypdf prior to 6.21.0

## Identifiers

- CVE-2026-113789
- GHSA-6vvc-x485-93v7

## Timeline

- 2026-10-21: disclosed
- 2026-10-16: patched

## References

- [https://github.com/py-pdf/pypdf/commit/5ef728f0e16d225c853e89f861ba0a67402fe3f2](https://github.com/py-pdf/pypdf/commit/5ef728f0e16d225c853e89f861ba0a67402fe3f2)
- [https://github.com/py-pdf/pypdf/pull/4219](https://github.com/py-pdf/pypdf/pull/4219)

## Related threats

- [pypdf memory exhaustion in cross-reference stream parsing](https://junglewise.ai/threats/cve-2026-119209-pypdf-is-a-free-and-open-source-pure-python-pdf-library-prior-to)
- [pypdf denial of service via forged encrypted PDF page count](https://junglewise.ai/threats/cve-2026-119208-pypdf-is-a-free-and-open-source-pure-python-pdf-library-prior-to)
- [pypdf excessive memory consumption in strict mode PDF parsing](https://junglewise.ai/threats/cve-2026-119207-pypdf-is-a-free-and-open-source-pure-python-pdf-library-prior-to)
- [pypdf denial of service via crafted page labels](https://junglewise.ai/threats/cve-2026-119206-pypdf-is-a-free-and-open-source-pure-python-pdf-library-prior-to)
- [pypdf infinite loop in DictionaryObject cloning](https://junglewise.ai/threats/cve-2026-119205-pypdf-is-a-free-and-open-source-pure-python-pdf-library-prior-to)