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. When the driver processes specially crafted IOCTL requests, it improperly manages stack memory, leading to a buffer overflow condition. This flaw can be exploited by an attacker with local access and low privileges (PR:L), without requiring user interaction or authentication. The overflow can corrupt the stack, potentially allowing arbitrary code execution with elevated privileges, compromising system confidentiality, integrity, and availability. The vulnerability does not require network access, limiting remote exploitation but increasing risk in environments where local access is possible, such as multi-user systems or those with exposed terminals. The vendor was notified early and has released a patch in version 3.0.0.1 to address the issue. The CVSS 4.0 vector (AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H) reflects the high impact on confidentiality, integrity, and availability, with low attack complexity and no user interaction required. Although no known exploits are currently in the wild, public disclosure increases the risk of exploitation attempts. Organizations using Nixdorf Wincor hardware or software that rely on this driver should urgently apply the patch to prevent potential local privilege escalation and system compromise.

For European organizations, the impact of CVE-2025-5555 can be significant, particularly in sectors where Nixdorf Wincor products are prevalent, such as banking, retail, and payment processing. Successful exploitation could allow local attackers to escalate privileges, execute arbitrary code, and potentially take full control of affected systems. This could lead to data breaches, disruption of critical services, and compromise of transaction integrity. Given the driver’s role in IO operations, exploitation might also affect system stability and availability, causing downtime or denial of service. In environments with shared access or insufficient physical security, the risk is heightened. The vulnerability’s local access requirement limits remote exploitation but does not eliminate risk in multi-user or physically accessible systems. European organizations with strict regulatory requirements around data protection and operational continuity could face compliance issues and reputational damage if exploited. The early availability of a patch mitigates long-term risk but requires prompt deployment to avoid exposure.

1. Immediately upgrade the Nixdorf Wincor PORT IO Driver to version 3.0.0.1 or later, as this version contains the patch addressing the buffer overflow vulnerability. 2. Restrict local access to systems running the affected driver by enforcing strict physical security controls and limiting user permissions to trusted personnel only. 3. Implement application whitelisting and endpoint protection solutions that can detect and block attempts to exploit local vulnerabilities. 4. Conduct regular audits of installed drivers and software versions on critical systems to ensure no outdated or vulnerable components remain. 5. Employ system hardening practices, including disabling unnecessary IOCTL interfaces if possible, to reduce the attack surface. 6. Monitor system logs and security alerts for unusual local activity that could indicate exploitation attempts. 7. Educate staff about the risks of local access exploitation and enforce policies to prevent unauthorized device or software installation. 8. In environments where patching is delayed, consider isolating affected systems or restricting access through network segmentation and access controls to minimize exposure.