CVE-2025-42978 is a vulnerability identified in the SAP NetWeaver Application Server Java, specifically affecting the ENGINEAPI 7.50 version. The issue stems from improper verification of the source of a communication channel, classified under CWE-940. The vulnerability arises because the component responsible for establishing outbound TLS connections does not reliably verify that the hostname used for the connection matches the wildcard hostname specified in the remote TLS server's certificate. This improper hostname verification can allow an attacker to impersonate a legitimate TLS server by presenting a certificate with a wildcard hostname that does not correctly match the intended destination hostname. Consequently, the SAP NetWeaver server might establish an outbound TLS connection to a malicious server controlled by an attacker. The primary risk here is the potential disclosure of sensitive information sent over this TLS connection, as the client may unknowingly communicate with an attacker’s server. However, the vulnerability does not impact the integrity or availability of the system or data. The CVSS v3.1 base score is 3.5, indicating a low severity level. Exploitation requires network access with low complexity, privileges (PR:L) are required, and user interaction is necessary (UI:R). No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability is significant because SAP NetWeaver is widely used in enterprise environments for critical business applications, and outbound TLS connections are common for integrations and data exchanges. Improper hostname verification undermines the trust model of TLS and can facilitate man-in-the-middle (MITM) attacks or data interception by malicious actors controlling rogue servers.

For European organizations, this vulnerability poses a risk primarily related to confidentiality breaches. Since SAP NetWeaver is extensively deployed across various industries including manufacturing, finance, and public sector entities in Europe, any interception of outbound TLS communications could lead to unauthorized disclosure of sensitive business data or personally identifiable information (PII). Although integrity and availability are not affected, the leakage of confidential data could have regulatory consequences under GDPR and other data protection laws prevalent in Europe. The risk is heightened in scenarios where SAP NetWeaver servers communicate with external partners or cloud services over TLS, as attackers could exploit this vulnerability to intercept or redirect sensitive data flows. The requirement for privileges and user interaction limits the ease of exploitation but does not eliminate the threat, especially in complex enterprise environments where multiple users and services interact. The absence of known exploits suggests the vulnerability is not yet actively targeted, but the potential impact on confidentiality means organizations should prioritize mitigation to prevent future exploitation.

European organizations should implement the following specific mitigation steps: 1) Monitor SAP’s official security advisories closely for patches or updates addressing CVE-2025-42978 and apply them promptly once available. 2) Review and harden TLS configuration on SAP NetWeaver Application Server Java instances, ensuring strict hostname verification is enforced where possible, potentially by customizing or extending the TLS client implementation to reject wildcard certificates that do not precisely match the intended hostname. 3) Implement network-level controls such as TLS interception proxies with strict certificate validation policies to detect and block suspicious outbound TLS connections that do not match expected hostnames or certificates. 4) Conduct internal audits of outbound TLS connections from SAP NetWeaver servers to identify unusual or unauthorized destinations. 5) Educate privileged users about the risks of this vulnerability and the importance of cautious interaction with SAP systems, minimizing unnecessary user interaction that could trigger exploitation. 6) Employ network segmentation and zero-trust principles to limit the exposure of SAP servers to untrusted networks and reduce the attack surface. 7) Utilize endpoint detection and response (EDR) tools to monitor for anomalous network activity indicative of MITM or rogue server connections.