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Download StationApplication · Synology

CVE-2021-34809

HIGH · 8.8 CVSS v3.1 Published 2021-06-18
Fix available
A fix is available. Upgrade to 3.8.16-3566 or later.
See remediation →
94/100
Remediation priority · Urgent
Remotely reachable Zero-click

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
Improper neutralization of special elements used in a command ('Command Injection') vulnerability in task management component in Synology Download Station before 3.8.16-3566 allows remote authenticated users to execute arbitrary code via unspecified vectors.

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

Command injection vulnerability in the task management component of Synology Download Station allows remote authenticated users to execute arbitrary OS commands through unspecified vectors. The vulnerability stems from improper neutralization of special elements in user-supplied input that gets passed to system commands.

MitigationUpgrade Synology Download Station to version 3.8.16-3566 or later which contains the fix for this command injection vulnerability. If immediate patching is not possible, restrict network access to the Download Station interface to trusted authenticated users only.

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
Download StationApplication
Affected:< 3.8.16-3566

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

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. Confirm Download Station is installed
    Log into Synology DSM and open Package Center, or run 'synopkg list' via SSH to see installed packages. Look for 'Download Station' in the package list.
    Affected if Download Station is not listed as installed - the vulnerability does not apply.
  2. Check Download Station version
    In DSM, go to Package Center > Download Station > Open. The version is displayed on the main page, or use 'synopkg info DownloadStation' via SSH.
    Affected if Version is present but less than 3.8.16-3566 - the system is vulnerable.
  3. Verify task management component is accessible
    Access Download Station via its web interface (usually port 5000/5001) and confirm the task management/queue feature is visible and functional. The vulnerability exists in this component.
    Affected if Task management features are available and the version is below 3.8.16-3566 - the vulnerability is present.
  4. Check user authentication configuration
    In DSM, go to Control Panel > User & Group to verify if remote authenticated users exist, or check Download Station settings for user access permissions.
    Affected if Remote user authentication is enabled and the Download Station version is below 3.8.16-3566 - the attack vector is viable.

A user is affected if Synology Download Station is installed with a version lower than 3.8.16-3566 and the task management interface is accessible to authenticated users.

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 3.8.16-3566 or later
Fixed in 3.8.16-3566
Interim mitigation

Upgrade Synology Download Station to version 3.8.16-3566 or later which contains the fix for this command injection vulnerability. If immediate patching is not possible, restrict network access to the Download Station interface to trusted authenticated users only.

Recommended fix High confidence

Download Station 3.8.16-3566 or later

  1. Log into your Synology NAS with administrator privileges
  2. Open Package Center
  3. Locate Download Station in the list of installed packages
  4. Click on Download Station and select 'Update' if an update is available
  5. Alternatively, check for DSM updates to ensure the latest packages are available
  6. Update to Download Station version 3.8.16-3566 or later
  7. Verify the update was successful by checking the version number in Package Center
Caveat Synology minor version updates typically have low risk but always backup critical data before updating

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

Fix this in Download Station Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.

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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-2021-34809 in production — separate from our analysis above.

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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