CVE-2025-4679 is a vulnerability identified in Synology's Active Backup for Microsoft 365 product. This vulnerability involves insufficient protection of credentials within the software, which allows remote authenticated attackers to obtain sensitive information. The attack requires the adversary to have valid credentials (remote authenticated access) but does not require user interaction. The vulnerability does not impact integrity or availability but has a high impact on confidentiality, as attackers can access sensitive credential data. The CVSS 3.1 base score is 6.5 (medium severity), with the vector AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N indicating network attack vector, low attack complexity, privileges required, no user interaction, unchanged scope, high confidentiality impact, and no integrity or availability impact. The exact vectors or methods of exploitation are unspecified, and no known exploits are reported in the wild as of the publication date. The affected versions are not specified, which suggests that the vulnerability may affect multiple or all current versions of the product. Synology Active Backup for Microsoft 365 is a backup solution designed to protect Microsoft 365 data, including emails, files, and other cloud data, by storing backups on Synology NAS devices. The vulnerability could allow attackers with valid credentials to extract backup credentials or other sensitive information, potentially enabling further unauthorized access or lateral movement within an organization's infrastructure.

For European organizations, this vulnerability poses a significant risk to the confidentiality of Microsoft 365 backup credentials and potentially other sensitive information stored or managed by Synology Active Backup for Microsoft 365. Compromise of these credentials could lead to unauthorized access to backup data, which may include sensitive corporate emails, documents, and other critical information. This could result in data breaches, exposure of personal data protected under GDPR, and potential compliance violations with European data protection regulations. Additionally, attackers leveraging this vulnerability could escalate privileges or move laterally within the network, increasing the risk of broader compromise. Organizations relying heavily on Synology NAS devices for Microsoft 365 backup, especially those in regulated sectors such as finance, healthcare, and government, could face operational disruptions and reputational damage if exploited.

1. Immediate patching: Although no specific patch links are provided, organizations should monitor Synology's official security advisories and promptly apply any released patches or updates addressing CVE-2025-4679. 2. Restrict access: Limit administrative and backup system access to trusted personnel only, enforcing the principle of least privilege to reduce the risk of credential compromise. 3. Network segmentation: Isolate Synology NAS devices and backup infrastructure from general user networks to reduce exposure to remote attacks. 4. Multi-factor authentication (MFA): Enforce MFA on all accounts with access to the backup system to mitigate risks from credential theft. 5. Credential management: Regularly rotate backup credentials and monitor for unusual access patterns or authentication attempts. 6. Logging and monitoring: Implement enhanced logging on Synology devices and backup systems to detect suspicious activities indicative of exploitation attempts. 7. Incident response readiness: Prepare and test incident response plans specific to backup infrastructure compromise scenarios. 8. Vendor engagement: Engage with Synology support for guidance and to confirm affected versions and remediation timelines.