CVE-2025-61915 is a vulnerability in the OpenPrinting CUPS (Common Unix Printing System) prior to version 2.4.15, caused by improper validation of array indices (CWE-129) leading to an out-of-bounds write (CWE-124). Specifically, a user with membership in the lpadmin group can access the cups web UI to alter the printing configuration by inserting a malicious line. When the cupsd daemon, which runs with root privileges, parses this manipulated configuration file, it performs an out-of-bounds write due to insufficient bounds checking on array indices. This memory corruption can lead to denial of service by crashing the cupsd process or potentially enable further exploitation depending on memory layout and system protections. The vulnerability requires local privilege (lpadmin group membership) but does not require user interaction. The CVSS 3.1 base score is 6.0 (medium severity), reflecting the local attack vector, low attack complexity, required privileges, no user interaction, and impact limited to availability (no confidentiality or integrity impact). No known exploits are reported in the wild as of publication. The issue was addressed in CUPS version 2.4.15 by adding proper validation to prevent out-of-bounds writes during config parsing.

For European organizations, this vulnerability could lead to denial of service of printing services on Linux/Unix systems running vulnerable CUPS versions. This can disrupt business operations, especially in environments heavily reliant on printing infrastructure such as government offices, healthcare, manufacturing, and financial institutions. Since the cupsd process runs as root, a crash or memory corruption could potentially be leveraged for privilege escalation or arbitrary code execution, although no such exploits are currently known. The requirement for lpadmin group membership limits the attack surface to authorized users or insiders, but insider threats or compromised accounts could exploit this. Organizations with large Linux server deployments or print servers are at higher risk. Disruption of printing services could impact document workflows and compliance processes, especially in regulated sectors. The vulnerability’s scope is limited to systems running vulnerable CUPS versions, so organizations using newer versions or alternative printing systems are unaffected.

European organizations should immediately verify the version of CUPS deployed on their Linux/Unix systems and upgrade to version 2.4.15 or later where this vulnerability is patched. Restrict membership of the lpadmin group to trusted administrators only, minimizing the number of users who can modify printing configurations. Implement strict access controls on the cups web UI, including network segmentation and firewall rules to limit access to trusted hosts and administrators. Monitor logs for unusual configuration changes or cupsd crashes that could indicate exploitation attempts. Employ host-based intrusion detection systems to detect anomalous behavior of the cupsd process. Regularly audit and update printing infrastructure components as part of patch management policies. Consider disabling the cups web UI if not required or replacing it with more secure management tools. Finally, educate administrators about the risks of configuration manipulation and the importance of applying security updates promptly.