NAS Under Siege: Critical 9.8 CVSS Bug in Synology Telnet Opens the Door to Total Hijack

Synology has issued an urgent security update for its DiskStation Manager (DSM) operating system to address a critical vulnerability in the Telnet service. The flaw, tracked as CVE-2026-32746, could allow unauthenticated remote attackers to bypass security layers and execute arbitrary commands on affected NAS devices.

The vulnerability carries a CVSS base score of 9.8, marking it as one of the most severe threats to the Synology ecosystem in recent months.

The root of the problem lies within the telnetd component of GNU Inetutils, a suite of common network utilities. Technically classified as CWE-120, the issue is a “Classic Buffer Overflow” occurring in the Set Local Characters (SLC) suboption handler.

According to the security advisory: “telnetd in GNU inetutils through 2.7 allows an out-of-bounds write… because add_slc does not check whether the buffer is full”.

By sending a specially crafted request, an attacker can overwrite system memory, leading to a complete takeover of the DiskStation without ever needing a username or password.

Synology has confirmed that multiple versions of its core operating systems are at risk. Owners of Synology hardware are strongly advised to verify their current version and update to the following fixed releases:

Other products, including BeeStation OS 1.4, SRM 1.3, and VS600HD 1.2, have been confirmed as “Not affected” by this specific vulnerability.

For users who cannot update their systems immediately, Synology provides a clear path to neutralize the threat. “It is recommended to disable the Telnet service to reduce potential risk”.

How to disable Telnet:

1. Navigate to the Control Panel.
2. Open the Terminal settings.
3. Uncheck the “Enable Telnet service” box.
4. Click Apply.

In modern secure environments, encrypted alternatives like SSH are preferred over Telnet, which transmits data in plain text. Disabling Telnet not only patches this specific vulnerability but also significantly hardens the overall security posture of your NAS.

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Do Son

Do Son (aka Ddos) is a seasoned news reporter, bringing over a decade of expertise to the forefront of cyber security and technology reporting. My work provides timely and insightful analysis of emerging trends and critical developments in these rapidly evolving sectors.