An insecure storage mechanism in Synology SSL VPN Client versions before 1.4.5‑0684 records the user’s PIN in plain text. This weakness allows an attacker to read or modify the PIN, which can in turn enable unauthorized configuration of the VPN or compromise the integrity of subsequent VPN traffic. The flaw is a password storage vulnerability, identified as CWE‑256.

Synology SSL VPN Client, all releases earlier than 1.4.5‑0684.

The CVSS score of 8.1 signals high severity. No EPSS data or KEV listing indicates that widespread exploitation has not yet been observed, although the vulnerability remains theoretically exploitable. Achieving the attack likely requires the attacker to gain access to the client on the user’s machine, such as through malicious software or local privilege escalation, to read or alter the stored PIN. Once the PIN is compromised, an attacker can configure the VPN or trick the user into accepting changes, which may allow interception or tampering of VPN traffic.