CVE-2025-9903 is an out-of-bounds write vulnerability (CWE-787) affecting multiple Canon Inc. Generic Plus printer drivers, including PCL6, UFR II, LIPS4, LIPSLX, and PS drivers, specifically versions 3.30 and earlier. This vulnerability arises during the print processing phase, where improper handling of input data allows an attacker to write data outside the intended memory boundaries. Such out-of-bounds writes can corrupt memory, potentially leading to arbitrary code execution, denial of service, or system instability. The vulnerability is remotely exploitable over the network (AV:N) but requires high attack complexity (AC:H), no privileges (PR:N), and user interaction (UI:R). The scope is unchanged (S:U), meaning the impact is limited to the vulnerable component. The CVSS v3.1 base score is 5.9, indicating a medium severity level. The impact primarily affects integrity (I:H) and availability (A:L), with no direct confidentiality impact (C:N). No known exploits are currently reported in the wild, and no patches have been linked yet. Given the nature of printer drivers, exploitation could occur when a user prints a malicious document or receives a malicious print job, triggering the vulnerability during processing. This could allow attackers to corrupt memory and potentially execute arbitrary code with the privileges of the user running the print spooler service, which often runs with elevated permissions on Windows systems. The vulnerability affects a broad range of Canon Generic Plus printer drivers, which are widely used in enterprise and office environments worldwide.

For European organizations, this vulnerability poses a significant risk to the integrity and availability of printing infrastructure. Printers are often critical components in office workflows, and compromise could lead to disruption of printing services, potentially halting business operations that rely on physical document output. Furthermore, successful exploitation could serve as a foothold for lateral movement within corporate networks, especially if the print spooler service runs with elevated privileges. This could escalate to broader compromise, data integrity issues, or denial of service conditions. Given the medium CVSS score and the requirement for user interaction, the risk is moderate but non-negligible. Organizations with heavy reliance on Canon printers, particularly those using the affected driver versions, are at greater risk. Additionally, sectors with strict regulatory requirements for data integrity and availability, such as finance, healthcare, and government, may face compliance challenges if this vulnerability is exploited. The lack of known exploits in the wild provides a window for proactive mitigation, but the potential for future exploitation remains.

European organizations should immediately inventory their printer fleet to identify devices using Canon Generic Plus printer drivers version 3.30 or earlier. Until official patches are released, organizations should consider the following specific mitigations: 1) Disable or restrict network printing capabilities to trusted users and devices only, minimizing exposure to untrusted print jobs. 2) Implement strict access controls on print servers and spooler services, ensuring only authenticated and authorized users can submit print jobs. 3) Employ network segmentation to isolate print servers and printers from critical network segments. 4) Monitor print server logs and network traffic for unusual or malformed print job submissions that could indicate exploitation attempts. 5) Educate users to avoid opening or printing documents from untrusted sources, as user interaction is required for exploitation. 6) Where feasible, temporarily replace vulnerable drivers with updated or alternative drivers not affected by this vulnerability. 7) Maintain up-to-date endpoint protection and intrusion detection systems to detect anomalous behavior related to print spooler exploitation. 8) Prepare for rapid deployment of patches once Canon releases official fixes, and test patches in controlled environments before wide deployment.