CVE-2025-5555 is a stack-based buffer overflow vulnerability identified in the Nixdorf Wincor PORT IO Driver, specifically affecting versions 1.0.0.0 and 1.0.0.1. The vulnerability resides in the IOCTL handler function sub_11100 within the wnport.sys driver library. This flaw allows an attacker with local access and low privileges to manipulate input to the IOCTL interface, causing a stack overflow. The overflow can overwrite critical control data on the stack, potentially enabling arbitrary code execution with elevated privileges or causing system crashes. The vulnerability does not require user interaction or authentication, increasing its risk profile in environments where local access is possible. The vendor was notified early and has released a patch in version 3.0.0.1 to address the issue. The CVSS 4.0 base score is 8.5, reflecting high impact on confidentiality, integrity, and availability, with low attack complexity and no need for user interaction. Although no known exploits are currently active in the wild, the public disclosure increases the risk of exploitation attempts. The affected driver is commonly used in Nixdorf Wincor hardware, which is prevalent in banking and retail sectors, especially in Europe. The vulnerability's exploitation could lead to privilege escalation, data theft, or denial of service, posing significant risks to critical infrastructure and sensitive data.

For European organizations, the impact of CVE-2025-5555 is significant due to the widespread use of Nixdorf Wincor systems in banking, retail, and financial services sectors. Exploitation could allow attackers with local access to escalate privileges, execute arbitrary code, and compromise system integrity and confidentiality. This could lead to unauthorized access to sensitive financial data, disruption of transaction processing, and potential service outages. Given the critical role of these systems in payment processing and ATM operations, successful exploitation could result in financial losses, reputational damage, and regulatory penalties under GDPR and other data protection laws. The local access requirement somewhat limits remote exploitation but insider threats or compromised endpoints could serve as vectors. The high severity and ease of exploitation necessitate urgent remediation to prevent potential attacks that could disrupt critical European financial infrastructure.

1. Immediate upgrade of the Nixdorf Wincor PORT IO Driver to version 3.0.0.1 or later, as provided by the vendor patch. 2. Restrict local access to systems running the affected driver by enforcing strict access controls and limiting administrative privileges. 3. Implement endpoint security solutions that monitor and alert on unusual IOCTL calls or attempts to interact with the wnport.sys driver. 4. Conduct thorough audits of systems to identify any presence of vulnerable driver versions and remove or isolate affected devices until patched. 5. Employ application whitelisting and driver signing enforcement to prevent unauthorized driver loading. 6. Train internal staff to recognize and report suspicious local activity that could indicate exploitation attempts. 7. Regularly review and update security policies to minimize the risk of insider threats and ensure rapid incident response capabilities. 8. Coordinate with vendors and cybersecurity authorities to stay informed about any emerging exploit techniques or additional patches.