CVE-2025-1021: Synology DSM Information Disclosure Flaw

CVE-2025-1021 Overview

CVE-2025-1021 is a missing authorization vulnerability discovered in the synocopy component of Synology DiskStation Manager (DSM). This flaw allows remote attackers to read arbitrary files on affected NAS devices without requiring authentication or any user interaction. The vulnerability stems from CWE-862 (Missing Authorization), indicating that critical authorization checks are absent from the affected functionality.

Critical Impact

Remote unauthenticated attackers can read arbitrary files from Synology NAS devices, potentially exposing sensitive configuration data, credentials, personal files, and other confidential information stored on the system.

Affected Products

• Synology DiskStation Manager (DSM) before version 7.1.1-42962-8
• Synology DiskStation Manager (DSM) before version 7.2.1-69057-7
• Synology DiskStation Manager (DSM) before version 7.2.2-72806-3

Discovery Timeline

• 2025-04-23 - CVE-2025-1021 published to NVD
• 2025-11-17 - Last updated in NVD database

Technical Details for CVE-2025-1021

Vulnerability Analysis

This vulnerability exists within the synocopy component of Synology DiskStation Manager, which handles file copy operations on DSM systems. The core issue is the complete absence of authorization checks when processing certain requests, allowing unauthenticated remote attackers to access and read arbitrary files from the file system.

The missing authorization flaw enables attackers to bypass normal access controls entirely. Since Synology NAS devices often store sensitive data including personal documents, backups, configuration files, and potentially credentials, the confidentiality impact is severe. Attackers can exploit this vulnerability remotely over the network without any prerequisites such as valid credentials or user interaction.

The vulnerability specifically affects the confidentiality of data on the system, with no direct impact on integrity or availability. However, information obtained through exploitation could facilitate further attacks against the compromised system or related infrastructure.

Root Cause

The root cause is CWE-862: Missing Authorization. The synocopy component fails to properly verify that requesting users or processes have appropriate permissions before allowing file read operations. This architectural oversight means that authorization checks that should validate access rights are either absent or improperly implemented, leaving the file access functionality exposed to unauthorized requests.

Attack Vector

The attack vector is network-based, requiring no privileges, no user interaction, and low attack complexity. An attacker with network access to the vulnerable DSM web interface can craft requests to the synocopy functionality to read files from the system. The attack can be executed remotely through unspecified vectors targeting the authorization bypass.

Since specific technical details regarding the exploitation vectors have not been publicly disclosed, organizations should refer to the Synology Security Advisory SA-25-03 for additional technical guidance and verify their systems are updated to patched versions.

Detection Methods for CVE-2025-1021

Indicators of Compromise

• Unusual or unexpected requests to synocopy endpoints in web server access logs
• Anomalous file read patterns or access attempts to sensitive directories from unauthenticated sessions
• Network traffic showing exploitation attempts against DSM management interfaces from untrusted sources
• Evidence of unauthorized file access in DSM audit logs or file access histories

Detection Strategies

• Monitor DSM access logs for requests to synocopy functionality from unauthorized or external IP addresses
• Implement network-based intrusion detection rules to identify exploitation attempts targeting DSM management interfaces
• Deploy file integrity monitoring on critical system configurations and sensitive data directories
• Review authentication logs for missing or bypassed authentication events associated with file operations

Monitoring Recommendations

• Enable comprehensive logging on all Synology DSM devices and forward logs to a centralized SIEM solution
• Configure alerts for any unauthenticated access attempts to DSM management services
• Monitor for unusual outbound data transfers that could indicate data exfiltration following exploitation
• Regularly audit DSM access logs for anomalous patterns indicating potential reconnaissance or exploitation attempts

How to Mitigate CVE-2025-1021

Immediate Actions Required

• Update Synology DiskStation Manager to version 7.1.1-42962-8 or later for DSM 7.1.x installations
• Update to version 7.2.1-69057-7 or later for DSM 7.2.1 installations
• Update to version 7.2.2-72806-3 or later for DSM 7.2.2 installations
• Restrict network access to DSM management interfaces to trusted networks only until patching is complete
• Review access logs for signs of prior exploitation

Patch Information

Synology has released security patches addressing this vulnerability across multiple DSM branches. Organizations should apply the appropriate update based on their current DSM version:

• DSM 7.1.x: Update to version 7.1.1-42962-8 or later
• DSM 7.2.1: Update to version 7.2.1-69057-7 or later
• DSM 7.2.2: Update to version 7.2.2-72806-3 or later

Refer to the Synology Security Advisory SA-25-03 for complete patch details and download links.

Workarounds

• Implement strict firewall rules to limit DSM web interface access to trusted IP addresses or internal networks only
• Place Synology NAS devices behind a VPN to prevent direct internet exposure of the management interface
• Disable any unnecessary DSM services or features that expose the system to network attacks
• Use network segmentation to isolate NAS devices from untrusted network segments

# Example: Restrict DSM access using iptables on upstream firewall
# Allow management access only from trusted management network
iptables -A INPUT -p tcp --dport 5000 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 5001 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 5000 -j DROP
iptables -A INPUT -p tcp --dport 5001 -j DROP