CVE-2026-22690 is a vulnerability classified under CWE-400 (Uncontrolled Resource Consumption) affecting the pypdf library, a widely used pure-Python PDF processing tool. The issue arises in versions prior to 6.6.0 when the library processes PDF files in non-strict reading mode. Specifically, if a PDF file is crafted without the mandatory /Root object in its trailer dictionary but includes a large /Size value, pypdf attempts to process an excessive number of objects, leading to prolonged runtimes. This can cause significant CPU and memory consumption, effectively resulting in a denial-of-service (DoS) condition. The vulnerability does not require any privileges, user interaction, or authentication, and can be exploited remotely by supplying a malicious PDF to an application using the vulnerable pypdf version. The flaw is due to insufficient validation of the trailer dictionary and the /Size parameter, which controls the number of indirect objects the parser attempts to read. The issue has been addressed in pypdf version 6.6.0 by adding proper validation and limiting resource consumption during parsing. No known exploits have been reported in the wild to date, but the vulnerability poses a risk to any automated system that processes untrusted PDF files using vulnerable pypdf versions.

For European organizations, the primary impact of this vulnerability is the risk of denial-of-service conditions in systems that rely on pypdf for PDF processing, such as document management systems, automated workflows, or web services that accept PDF uploads. Attackers can exploit this flaw to degrade service availability by sending specially crafted PDFs that cause excessive resource consumption. This can lead to increased CPU usage, memory exhaustion, and potential service outages, affecting business continuity and user experience. Confidentiality and integrity are not directly impacted, but availability degradation can disrupt critical document processing operations. Organizations handling large volumes of PDFs or providing PDF-related services are particularly at risk. Additionally, sectors with high reliance on automated document workflows, such as finance, legal, and government agencies, may face operational disruptions. While the CVSS score is low, the ease of exploitation and potential for service disruption warrant attention, especially in environments processing untrusted or external PDF files.

To mitigate this vulnerability, European organizations should immediately upgrade all instances of pypdf to version 6.6.0 or later, where the issue is patched. Additionally, implement strict input validation and sanitization for all PDF files before processing, including rejecting PDFs missing mandatory structural elements like the /Root object. Employ resource usage monitoring and limits on PDF parsing operations to detect and prevent excessive CPU or memory consumption. Consider running PDF processing tasks in isolated environments or containers with resource constraints to limit the impact of potential abuse. For web-facing services, apply rate limiting and file size restrictions on PDF uploads to reduce attack surface. Regularly audit and update dependencies to ensure all libraries are current and vulnerabilities are addressed promptly. Finally, educate developers and system administrators about this vulnerability to ensure awareness and proactive defense.