CVE-2025-42959 is a high-severity vulnerability affecting multiple versions of SAP NetWeaver ABAP Server and ABAP Platform, specifically SAP_BASIS versions ranging from 700 through 915. The vulnerability stems from the use of single-factor authentication mechanisms that rely on Hashed Message Authentication Code (HMAC) credentials. An attacker who has previously extracted an HMAC credential from a system lacking specific security patches can reuse this credential in a replay attack against a different system, even if the target system is fully patched. This replay attack bypasses authentication controls, allowing an unauthenticated attacker to gain unauthorized access. Successful exploitation can lead to complete system compromise, impacting confidentiality, integrity, and availability of the affected SAP systems. The vulnerability is classified under CWE-308, which relates to the use of single-factor authentication, indicating that the authentication mechanism is insufficiently robust. The CVSS v3.1 base score is 8.1, reflecting a high severity due to network attack vector, no privileges required, no user interaction, and high impact on confidentiality, integrity, and availability. No known exploits are currently reported in the wild, and no patches have been linked yet, emphasizing the need for proactive mitigation. This vulnerability is particularly critical because SAP NetWeaver ABAP Server and ABAP Platform are widely used enterprise resource planning (ERP) components integral to business operations, making them attractive targets for attackers seeking to disrupt or steal sensitive business data.

For European organizations, the impact of CVE-2025-42959 could be severe. SAP systems are extensively deployed across various industries in Europe, including manufacturing, finance, utilities, and public sector entities. A successful replay attack exploiting this vulnerability could lead to unauthorized access to critical business applications, resulting in data breaches involving sensitive personal data (subject to GDPR), intellectual property theft, operational disruption, and potential financial losses. The compromise of SAP systems could also undermine trust in business processes and lead to regulatory penalties. Given the high integration of SAP platforms in supply chains and critical infrastructure, the availability impact could cause significant operational downtime. Furthermore, the ability to bypass authentication without user interaction or privileges increases the risk of automated or large-scale attacks, potentially affecting multiple organizations simultaneously.

To mitigate this vulnerability effectively, European organizations should: 1) Immediately identify and inventory all SAP NetWeaver ABAP Server and ABAP Platform instances, focusing on the affected SAP_BASIS versions listed. 2) Apply all relevant SAP security patches and updates as soon as they become available, prioritizing systems that have not yet been patched. 3) Implement multi-factor authentication (MFA) mechanisms to replace or augment single-factor HMAC-based authentication, reducing the risk of replay attacks. 4) Monitor network traffic for unusual authentication attempts or replay attack patterns, employing anomaly detection tools tailored for SAP environments. 5) Restrict network access to SAP systems using segmentation and firewall rules to limit exposure to untrusted networks. 6) Conduct regular security audits and penetration testing focused on authentication mechanisms within SAP systems. 7) Educate SAP administrators and security teams about the risks of credential reuse and replay attacks to ensure vigilant operational practices. 8) Consider deploying SAP-specific security tools that can detect and prevent replay attacks or credential misuse. These steps go beyond generic advice by focusing on SAP-specific controls and proactive monitoring tailored to the nature of the vulnerability.