Synology Network File System Vulnerability Allows Unauthorized File Access

A critical security vulnerability in Synology’s Network File System (NFS) service, tracked as CVE-2025-1021, has been resolved after allowing unauthorized remote attackers to access sensitive files on vulnerable DiskStation Manager (DSM) devices.

The flaw, marked as “Important” in severity by Synology, affects several versions of DSM, the operating system powering the company’s popular Network Attached Storage (NAS) solutions.

Vulnerability Details

The issue centers around a missing authorization check in the synocopy component of DSM.

According to Synology’s security advisory Synology-SA-25:03, the vulnerability permits unauthenticated attackers to read arbitrary files via a writable NFS service, potentially exposing confidential information.

The Common Vulnerability Scoring System (CVSS v3.1) rates this risk at 7.5 out of 10, underlining its seriousness.

Crucially, the attack does not require any user interaction or authentication, enabling exploitation by remote threat actors.

Successful attacks could lead to severe data leakage, including personal files, business documents, and other sensitive data stored on NAS devices.

Aspect	Details
Vulnerability ID	CVE-2025-1021
Product	Synology DiskStation Manager (DSM)
Component	synocopy (NFS Service)
Severity	Important
CVSS v3.1 Score	7.5

Affected Products and Fixes

The vulnerability is present in the following DSM versions:

• DSM 7.2.2 — Fixed in 7.2.2-72806-3 and later
• DSM 7.2.1 — Fixed in 7.2.1-69057-7 and later
• DSM 7.1 — Fixed in 7.1.1-42962-8 and later

Synology recommends that all users immediately upgrade to the latest patched versions. No mitigation strategy is available other than applying the update.

This issue was responsibly disclosed by the DEVCORE Research Team (https://devco.re/), who identified the flaw and reported it to Synology.

The advisory was first released on February 26, 2025, with full vulnerability details disclosed on April 23, 2025, after patches were made available.

Owners of Synology NAS devices running affected versions of DSM are strongly urged to upgrade as soon as possible to avoid unauthorized access to their stored files.

Organizations using exposed NFS services should be particularly vigilant, as exploitation does not require any special access credentials.

This vulnerability highlights the importance of regular updates and monitoring of NAS environments, especially those accessible over network file systems.

Synology’s swift response and the coordinated disclosure with security researchers have helped to minimize the potential impact, but the incident serves as a reminder that NAS security is critical in protecting sensitive data in homes and businesses alike.

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