CVE-2026-84311: CWE-834: Excessive Iteration in py-pdf pypdf
Description
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._extract_text and PageObject.extract_xform_text to traverse a directed acyclic graph of reused form XObjects in which each form invokes a child multiple times, creating exponentially many traversal paths and causing long runtimes and large memory consumption. This issue is fixed in version 6.16.1.
CVSS v4.0
Score 4.8medium
Affected software
py-pdf
pypdf
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in pypdf affects the PageObject._extract_text and PageObject.extract_xform_text methods, which traverse a directed acyclic graph of reused form XObjects. An attacker can craft a PDF where each form invokes a child multiple times, causing an exponential increase in traversal paths. This excessive iteration leads to performance degradation through long runtimes and large memory usage. The flaw is addressed in version 6.16.1 of pypdf.
Potential Impact
Exploitation of this vulnerability can cause denial of service conditions due to resource exhaustion (CPU and memory) when processing maliciously crafted PDFs. There is no indication of code execution, data disclosure, or privilege escalation. The impact is limited to performance degradation and potential application unavailability during PDF text extraction.
Mitigation Recommendations
Upgrade to pypdf version 6.16.1 or later, where this vulnerability is fixed. Since no official patch link or advisory is provided, verify the upgrade through the official pypdf release notes or repository. No other mitigation is indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-09-01T16:17:43.079Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a973451acd9273b492939be
Added to database: 09/01/2026, 20:23:45 UTC
Last enriched: 09/07/2026, 13:45:48 UTC
Last updated: 10/17/2026, 18:48:23 UTC
Views: 77
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