Infinite loop Affecting pypdf package, versions [3.1.0,6.13.1)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PYTHON-PYPDF-17420043
- published23 Jun 2026
- disclosed22 Jun 2026
- creditk0w4lzk1
Introduced: 22 Jun 2026
NewCVE-2026-54651 (opens in a new tab)How to fix?
Upgrade pypdf to version 6.13.1 or higher.
Overview
pypdf is an A pure-python PDF library capable of splitting, merging, cropping, and transforming PDF files
Affected versions of this package are vulnerable to Infinite loop through the _add_articles_thread method in PdfWriter when processing PDF thread/article structures. An attacker can trigger an infinite loop by supplying a PDF with a cyclic /F//N article chain that is cloned while writing or filtering threads. This can hang the application and prevent users from completing PDF processing, consuming CPU until the request or process is terminated.
Workarounds
- If you cannot upgrade yet, apply the changes from PR
#3839to your localpypdfcheckout soPdfWriterno longer loops indefinitely when merging files that contain threads/articles.