CVE-2026-24688 is a vulnerability classified under CWE-835 (Loop with Unreachable Exit Condition) affecting the pypdf library, a widely used pure-Python PDF processing tool. Versions of pypdf prior to 6.6.2 contain a flaw in the handling of PDF outlines/bookmarks, where a specially crafted PDF can cause the library to enter an infinite loop. This infinite loop results from a logic error in the iteration or parsing of the outline structure, preventing normal termination of the loop. The consequence is a denial of service (DoS) condition, as the process consuming the PDF becomes unresponsive or consumes excessive CPU resources. The vulnerability does not require any privileges or user interaction but requires that the malicious PDF be processed by the vulnerable pypdf version. The issue was resolved in version 6.6.2 by correcting the loop condition logic, and a pull request (#3610) contains the patch. Since pypdf is often embedded in various Python applications and services that handle PDF files, this vulnerability could be exploited by attackers to disrupt service availability by supplying crafted PDFs. No public exploits have been reported to date, but the medium CVSS score of 5.1 reflects the moderate impact and ease of exploitation given local access to the PDF file.

For European organizations, the primary impact of CVE-2026-24688 is the risk of denial of service in applications or services that utilize vulnerable versions of pypdf to process PDF documents. This could affect document management systems, automated PDF processing pipelines, web applications allowing PDF uploads, or any internal tools relying on pypdf. Disruption of these services could lead to operational downtime, reduced productivity, and potential reputational damage, especially in sectors heavily reliant on document workflows such as finance, legal, healthcare, and government. While the vulnerability does not directly compromise confidentiality or integrity, the availability impact could be significant if exploited at scale or in critical environments. The lack of known exploits reduces immediate risk, but the ease of crafting malicious PDFs means attackers could weaponize this vulnerability in targeted attacks or spam campaigns. European organizations with strict uptime requirements or regulatory obligations around service availability should consider this vulnerability a moderate threat.

European organizations should prioritize upgrading all instances of pypdf to version 6.6.2 or later to fully remediate the vulnerability. If immediate upgrading is not possible due to compatibility or operational constraints, applying the patch from pull request #3610 manually is recommended to fix the infinite loop condition. Additionally, organizations should implement input validation and sandboxing for PDF processing workflows to limit the impact of malicious PDFs. Rate limiting and resource usage monitoring on services handling PDFs can help detect and mitigate denial of service attempts. Employing application-level timeouts or watchdog mechanisms to terminate processes stuck in infinite loops can reduce service disruption. Regularly auditing software dependencies and maintaining an up-to-date inventory of pypdf usage across internal and external applications will aid in comprehensive mitigation. Finally, educating developers and system administrators about this vulnerability will ensure timely patching and response.