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Mail StationApplication · Synology

CVE-2021-43928

HIGH · 8.8 CVSS v3.1 Published 2022-02-07
Fix available
A fix is available. Upgrade to 20211105 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 an OS command ('OS Command Injection') vulnerability in mail sending and receiving component in Synology Mail Station before 20211105-10315 allows remote authenticated users to execute arbitrary commands 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

This is an OS command injection vulnerability in Synology Mail Station's mail sending and receiving component. A remote authenticated user can inject and execute arbitrary operating system commands through unspecified vectors in the mail handling functionality. The vulnerability exists in versions prior to 20211105-10315.

MitigationUpdate Synology Mail Station to version 20211105-10315 or later. If immediate patching is not possible, restrict access to the mail service to trusted users and monitor for suspicious mail activity that could indicate exploitation attempts.

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
Mail StationApplication
Affected:< 20211105

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 Synology Mail Station is installed
    Access Synology DiskStation Manager (DSM), navigate to Package Center, and look for Mail Station in the installed package list
    Affected if Mail Station is not listed as installed - the system is not affected because the vulnerable component is not present
  2. Determine the installed version of Mail Station
    In DSM Package Center, click on Mail Station and view the version information displayed, or use the command line and query the Synology package management system for the installed Mail Station package version
    Affected if Unable to retrieve version information - cannot determine if the installation is vulnerable
  3. Compare installed version to affected range
    Check if the installed version is earlier than 20211105-10315. Note that the affected range is any version prior to 20211105-10315
    Affected if Installed version is less than 20211105-10315 - the system is vulnerable to command injection through the mail handling component
  4. Verify mail handling component is enabled
    In DSM, navigate to Mail Station settings and confirm that the mail sending and receiving functionality is enabled and configured
    Affected if Mail sending/receiving is not configured or enabled - the attack surface may be reduced but the vulnerability still exists in the software version if installed
  5. Assess network exposure of the mail service
    Review firewall rules and network settings to determine if the Mail Station web interface or associated services are accessible from untrusted networks
    Affected if Mail Station is exposed to untrusted networks without proper access controls - increases the risk of exploitation by remote authenticated attackers

The environment is affected if Synology Mail Station is installed with any version earlier than 20211105-10315, regardless of whether mail handling is actively used, since the vulnerable code exists in the installed package.

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 20211105 or later
Fixed in 20211105
Interim mitigation

Update Synology Mail Station to version 20211105-10315 or later. If immediate patching is not possible, restrict access to the mail service to trusted users and monitor for suspicious mail activity that could indicate exploitation attempts.

Recommended fix High confidence

Mail Station version 20211105-10315 or later

  1. 1. Log in to Synology DiskStation Manager (DSM) as an administrator.
  2. 2. Navigate to Package Center to view installed packages.
  3. 3. Locate Synology Mail Station in the installed packages list.
  4. 4. Click on Mail Station and check the current version installed.
  5. 5. If the version is earlier than 20211105-10315, click Update to install the latest available version.
  6. 6. Wait for the update to complete and verify the new version is 20211105-10315 or later.
  7. 7. Review Synology Mail Station settings to ensure proper functionality after update.
Caveat Standard Synology package update - backup mail data before major updates as a precaution

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

Fix this in Mail Station Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,224.

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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-2021-43928 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