CVE-2025-6644 is a high-severity use-after-free vulnerability (CWE-416) found in PDF-XChange Editor version 10.5.2.395, specifically in the parsing of U3D (Universal 3D) files embedded within PDFs. The vulnerability arises because the software fails to validate the existence of an object before performing operations on it during U3D file parsing. This improper handling leads to a use-after-free condition, which attackers can exploit to execute arbitrary code remotely in the context of the current process. Exploitation requires user interaction, such as opening a maliciously crafted PDF file or visiting a malicious webpage that triggers the vulnerability. The CVSS v3.0 base score is 7.8, reflecting high impact on confidentiality, integrity, and availability, with attack vector local (AV:L), low attack complexity (AC:L), no privileges required (PR:N), user interaction required (UI:R), unchanged scope (S:U), and high impact on confidentiality (C:H), integrity (I:H), and availability (A:H). No known exploits are currently reported in the wild, but the vulnerability was publicly disclosed on June 25, 2025, and tracked under ZDI-CAN-26536. The lack of a patch link indicates that a fix may not yet be available or publicly released at the time of this report. Given the nature of the vulnerability, successful exploitation could allow attackers to execute arbitrary code, potentially leading to full system compromise or data theft on affected systems running the vulnerable PDF-XChange Editor version.

For European organizations, this vulnerability poses a significant risk, especially in sectors heavily reliant on PDF documents for communication and documentation, such as finance, legal, government, and healthcare. Since PDF-XChange Editor is a popular PDF viewer/editor alternative to Adobe Acrobat, organizations using this product are at risk of targeted attacks via malicious PDF files delivered through email phishing campaigns or compromised websites. Successful exploitation could lead to remote code execution, enabling attackers to deploy malware, ransomware, or conduct espionage activities. The high impact on confidentiality, integrity, and availability means sensitive data could be exfiltrated, altered, or destroyed, disrupting business operations and damaging reputations. The requirement for user interaction means social engineering remains a key attack vector, emphasizing the need for user awareness. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, as attackers often develop exploits rapidly after public disclosure. European organizations with strict data protection regulations (e.g., GDPR) could face compliance issues and penalties if breaches occur due to this vulnerability.

1. Immediate mitigation should include disabling or restricting the use of PDF-XChange Editor version 10.5.2.395 until a vendor patch is available. 2. Employ application whitelisting to prevent execution of unauthorized or suspicious PDF files. 3. Use network-level protections such as email filtering and web proxy solutions to block or quarantine emails and downloads containing suspicious PDFs, particularly those with embedded U3D content. 4. Educate users to recognize phishing attempts and avoid opening unsolicited or unexpected PDF attachments or links. 5. Monitor endpoint behavior for unusual process activity or crashes related to PDF-XChange Editor, which could indicate exploitation attempts. 6. Consider deploying sandboxing or isolated environments for opening untrusted PDF files to contain potential exploitation. 7. Once a patch is released by the vendor, prioritize rapid testing and deployment across all affected systems. 8. Maintain up-to-date backups and incident response plans to mitigate impact in case of successful exploitation.