CVE-2025-59258 is a vulnerability identified in Microsoft Windows Server 2019, specifically affecting the Active Directory Federation Services (AD FS) component. The issue is classified under CWE-532, which involves the insertion of sensitive information into log files. In this case, AD FS improperly logs sensitive data locally, potentially including authentication tokens, credentials, or other confidential information. Because these logs are accessible on the local system, an attacker who gains local access—without needing privileges or user interaction—can read these logs and extract sensitive information. The vulnerability has a CVSS v3.1 base score of 6.2, indicating a medium severity level. The attack vector is local (AV:L), with low attack complexity (AC:L), no privileges required (PR:N), and no user interaction (UI:N). The impact is high on confidentiality (C:H), but no impact on integrity or availability. This vulnerability does not currently have known exploits in the wild, and no patches have been published yet. However, the presence of sensitive data in logs can facilitate further attacks such as privilege escalation or lateral movement if an attacker gains initial local access. The vulnerability was reserved in September 2025 and published in October 2025, indicating recent discovery. AD FS is widely used in enterprise environments for federated identity management, making this vulnerability relevant for organizations that rely on Windows Server 2019 for authentication services.

For European organizations, the primary impact is the potential disclosure of sensitive authentication information stored in AD FS logs on Windows Server 2019 systems. This can lead to unauthorized disclosure of credentials or tokens, enabling attackers to escalate privileges or move laterally within corporate networks. Confidentiality breaches can result in data leaks, regulatory non-compliance (e.g., GDPR), and reputational damage. Since exploitation requires local access, the threat is heightened in environments where physical or remote local access is possible, such as shared hosting, poorly secured data centers, or compromised endpoints. Organizations with extensive AD FS deployments for single sign-on and federated identity are particularly vulnerable. The vulnerability does not affect system integrity or availability directly but can be a stepping stone for more severe attacks. The lack of known exploits currently reduces immediate risk, but the medium severity score suggests timely mitigation is important to prevent future exploitation.

1. Restrict local access to Windows Server 2019 systems running AD FS to trusted personnel only, using strong physical and logical access controls. 2. Implement strict file system permissions on log directories to prevent unauthorized reading of log files containing sensitive information. 3. Monitor and audit access to AD FS log files for unusual or unauthorized access patterns. 4. Consider disabling or limiting verbose logging in AD FS if feasible, to reduce sensitive data exposure in logs. 5. Apply any Microsoft patches or security updates promptly once released for this vulnerability. 6. Use endpoint detection and response (EDR) tools to detect suspicious local activity that could indicate attempts to access sensitive logs. 7. Employ network segmentation to limit lateral movement opportunities if credentials are compromised. 8. Educate system administrators about the risks of sensitive data in logs and the importance of secure log management. 9. Review and enhance overall AD FS security configurations, including multi-factor authentication and monitoring of authentication events. 10. Prepare incident response plans to quickly address potential data disclosures stemming from this vulnerability.