CVE-2025-1021 is a critical vulnerability affecting Synology DiskStation Manager (DSM), specifically its Network File System (NFS) service. This flaw allows unauthenticated remote attackers to read arbitrary files on vulnerable devices, posing a significant risk to data confidentiality.
1. Vulnerability Overview
Description
The vulnerability stems from missing authorization checks in the synocopy module of DSM, which handles file operations over NFS. Under normal operation, NFS exports enforce access controls such as IP allow lists, user mapping, and read/write permissions. However, due to this flaw, these safeguards can be bypassed entirely.
Attackers can exploit this vulnerability by issuing specially crafted NFS requests to writable shares, enabling them to access files outside the exported directory. This includes sensitive system files (e.g., /etc/shadow), application data, and user home directories.
Severity
- CVSS Score: 7.5 (High).
- Attack Vector: Network (AV:N).
- Attack Complexity: Low (AC:L).
- Privileges Required: None (PR:N).
- User Interaction: None (UI:N).
- Confidentiality Impact: High (C:H).
- Integrity and Availability Impact: None (I:N/A:N).
2. Affected Versions
The vulnerability affects the following DSM versions:
- DSM 7.1.1-42962-8 and earlier.
- DSM 7.2.1-69057-7 and earlier.
- DSM 7.2.2-72806-3 and earlier.
3. Exploitation Details
How It Works
- Attackers target writable NFS shares exposed by vulnerable DSM devices.
- By sending malformed NFS requests, they bypass authorization checks and gain access to arbitrary files.
- The flaw effectively turns any writable share into an unauthenticated data leak, allowing attackers to harvest sensitive information.
Potential Impact
- Data Exposure: Attackers can access sensitive files, including credentials, intellectual property, and private user data.
- Compliance Violations: Organizations may face regulatory penalties due to unauthorized data access.
- Ransomware Risk: Exposed data could be leveraged for ransomware attacks or identity theft.
4. Mitigation Strategies
A. Apply Security Patches
Synology has released patches to address CVE-2025-1021. Users should immediately update their DSM devices to the following versions:
- DSM 7.1.1-42962-9 or later.
- DSM 7.2.1-69057-8 or later.
- DSM 7.2.2-72806-4 or later.
B. Restrict NFS Access
- Limit NFS access to trusted IP addresses using DSM’s built-in firewall settings.
- Disable NFS services if not actively required.
C. Monitor for Exploitation
- Audit system logs for unusual NFS activity, such as unauthorized file access attempts.
- Deploy Intrusion Detection Systems (IDS) to flag suspicious network traffic targeting NFS shares.
D. Strengthen Network Security
- Use VPNs to secure remote access to DSM devices.
- Enforce strong passwords and enable multi-factor authentication (MFA) for administrative accounts.
5. Conclusion
CVE-2025-1021 highlights the importance of robust authorization mechanisms in network-attached storage (NAS) devices. Organizations and individuals using Synology DSM must act swiftly to patch their systems and implement access controls to mitigate risks.
For more technical details, you can find Synology’s official advisory here.
