dbcve.org
Ssl Vpn ClientApplication · Synology

CVE-2021-47961

HIGH · 8.1 CVSS v3.1 Published 2026-04-10
Fix available
A fix is available. Upgrade to 1.4.5-0684 or later.
See remediation →
88/100
Remediation priority · High
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A plaintext storage of a password vulnerability in Synology SSL VPN Client before 1.4.5-0684 allows remote attackers to access or influence the user's PIN code due to insecure storage. This may lead to unauthorized VPN configuration and potential interception of subsequent VPN traffic when combined with user interaction.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The Synology SSL VPN Client before version 1.4.5-0684 stores user PIN codes in plaintext or with insufficient protection, allowing remote attackers who can access the client system to retrieve these credentials. Combined with user interaction, this enables unauthorized VPN configuration changes and potential traffic interception.

MitigationUpdate Synology SSL VPN Client to version 1.4.5-0684 or later, which implements proper encryption for stored credentials. Organizations should also audit VPN configurations for any unauthorized changes after patching.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Ssl Vpn ClientApplication
Affected:< 1.4.5-0684

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if Synology SSL VPN Client is installed
    Check the system for the presence of Synology SSL VPN Client application files or registry entries. Common locations include Program Files directories on Windows or Application folders on macOS. Use system inventory or software listing tools to confirm installation.
    Affected if The Synology SSL VPN Client application is found on the system
  2. Determine the installed version
    Locate the version information for the installed Synology SSL VPN Client. This is typically available through the application UI (Help > About), or by checking file properties of the main executable. Compare the version number against 1.4.5-0684.
    Affected if The installed version is lower than 1.4.5-0684
  3. Inspect credential storage location
    Examine the application data directory for the Synology SSL VPN Client. Look for configuration files, preference files, or credential stores where PIN codes might be saved. Check if these files contain plaintext PIN codes or use weak/obfuscated storage rather than proper encryption.
    Affected if PIN codes or VPN credentials are found stored in plaintext or with weak protection in application data directories
  4. Review VPN configuration for unauthorized changes
    Audit the current VPN configuration profiles managed by the Synology SSL VPN Client. Check for any unexpected server addresses, altered authentication settings, or new configuration profiles that were not created by the legitimate administrator.
    Affected if VPN configurations show unexpected changes, new profiles, or connections to unknown servers

A system is affected if Synology SSL VPN Client version lower than 1.4.5-0684 is installed and plaintext or weakly protected PIN codes are present in the application storage area.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.4.5-0684 or later
Fixed in 1.4.5-0684
Interim mitigation

Update Synology SSL VPN Client to version 1.4.5-0684 or later, which implements proper encryption for stored credentials. Organizations should also audit VPN configurations for any unauthorized changes after patching.

Recommended fix High confidence

1.4.5-0684 or later

  1. Download the latest version of Synology SSL VPN Client (version 1.4.5-0684 or later) from the official Synology website
  2. Uninstall the current vulnerable version of Synology SSL VPN Client
  3. Install the updated version 1.4.5-0684 or later
  4. Re-enter VPN credentials and PIN code as needed after the upgrade

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Ssl Vpn Client Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-47961 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data