CVE-2025-46206 is a vulnerability identified in Artifex MuPDF versions 1.25.5 and 1.25.6, specifically affecting the 'mutool clean' utility. The issue arises from the way the utility processes PDF files with crafted outline structures containing cyclic /Next references. In such cases, the 'strip_outline()' function enters into infinite recursion due to the cyclic references, leading to a denial of service (DoS) condition. This vulnerability is classified under CWE-674 (Improper Control of a Resource Through a Reference Cycle), indicating that the software fails to properly handle cyclic data structures, resulting in resource exhaustion. The attack vector is remote and requires no privileges but does require user interaction (opening or processing a malicious PDF file). The CVSS v3.1 base score is 6.5 (medium severity), with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), user interaction required (UI:R), unchanged scope (S:U), no impact on confidentiality or integrity (C:N/I:N), and high impact on availability (A:H). The vulnerability does not appear to have known exploits in the wild yet, and no patches are currently linked, indicating that affected users should be cautious and monitor for updates. The core technical issue is the infinite recursion caused by cyclic references in the PDF outline, which can cause the utility to hang or crash, denying service to legitimate users or automated processes relying on mutool clean for PDF sanitization or processing.

For European organizations, the primary impact of this vulnerability is the potential disruption of services or workflows that utilize the mutool clean utility for PDF processing, especially in automated document handling, archival, or sanitization pipelines. Since the vulnerability causes a denial of service without compromising confidentiality or integrity, the risk is mainly operational. Organizations that rely on MuPDF tools for document management, legal, financial, or governmental document processing could face downtime or delays if targeted with crafted malicious PDFs. Additionally, sectors with high PDF usage such as publishing, education, and public administration may experience interruptions. While the vulnerability does not allow code execution or data leakage, the denial of service could be exploited as part of a broader attack to disrupt operations or delay critical document processing. The requirement for user interaction (opening or processing the malicious PDF) somewhat limits the attack surface but does not eliminate risk, especially in environments where PDFs are received from external or untrusted sources.

European organizations should implement several specific mitigations: 1) Avoid using affected versions (1.25.5 and 1.25.6) of MuPDF's mutool clean utility until a patch is released. 2) Employ strict input validation and sandboxing for PDF files before processing them with mutool clean, including scanning for cyclic references or malformed outline structures using alternative PDF analysis tools. 3) Restrict the use of mutool clean to trusted PDF sources and implement user training to recognize suspicious PDF files. 4) Monitor PDF processing workflows for unusual hangs or crashes indicative of infinite recursion. 5) Consider deploying rate limiting or timeout mechanisms on mutool clean executions to prevent resource exhaustion from infinite recursion. 6) Stay updated with Artifex's security advisories for patches or workarounds. 7) As a longer-term measure, evaluate alternative PDF processing tools with better resilience against cyclic reference issues. These steps go beyond generic advice by focusing on controlling input quality, operational monitoring, and limiting exposure to untrusted PDFs.