dbcve.org
Active Backup For Microsoft 365Application · Synology

CVE-2025-4679

MEDIUM · 6.5 CVSS v3.1 Published 2025-05-16
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
71/100
Remediation priority · Elevated
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
A vulnerability in Synology Active Backup for Microsoft 365 allows remote authenticated attackers to obtain sensitive information 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 · moderate confidence

Synology Active Backup for Microsoft 365 contains an information disclosure vulnerability that allows remote authenticated attackers to obtain sensitive information. The attack requires authentication, indicating the vulnerability likely involves improper access controls or data sanitization within the backup application. The specific attack vectors are unspecified in the advisory.

MitigationApply the vendor patch when available. Until then, restrict network access to the Active Backup service to trusted users only, and monitor for unauthorized access attempts using authentication logs.

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
Active Backup For Microsoft 365Application
Affected:all versions

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
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/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. Confirm Active Backup for Microsoft 365 is installed
    Access Synology DSM and navigate to Package Center to verify if the Active Backup for Microsoft 365 package is installed. Alternatively, run the command 'grep -i "active backup" /var/log/synopkg.log' on the Synology NAS to check installation status.
    Affected if The package is listed as installed in Package Center or appears in the package logs.
  2. Identify network exposure of the Active Backup service
    Check Synology DSM under Control Panel > Security > Firewall to see if inbound rules allow access to ports used by Active Backup (typically ports 30000-30100 or custom ports). Also verify if the DSM is directly accessible from external IPs without VPN.
    Affected if Firewall rules permit untrusted or public IP addresses to reach the Active Backup service ports.
  3. Review authentication logs for the backup portal
    In Synology DSM, go to Log Center and filter logs for 'Active Backup' or 'ABM365' entries. Look for authentication events, especially from unfamiliar IP addresses or at unusual times.
    Affected if Logs show successful authentications from IP addresses that are not recognized or expected.
  4. Check for unauthorized backup job modifications
    In Active Backup for Microsoft 365, navigate to the Task List and review all configured backup tasks. Verify that no new tasks were created or existing tasks modified without authorization.
    Affected if New or modified backup tasks exist that were not created by an authorized administrator.
  5. Inspect user access controls on the backup service
    In Active Backup for Microsoft 365, go to Settings > User Account Access or the equivalent permission panel. Review the list of users granted access to the backup service and confirm all are authorized personnel.
    Affected if Unrecognized user accounts or excessive permissions are assigned to the Active Backup service.

The environment is affected if Synology Active Backup for Microsoft 365 is installed and accessible to untrusted network users, regardless of version since all versions are vulnerable.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the vendor patch when available. Until then, restrict network access to the Active Backup service to trusted users only, and monitor for unauthorized access attempts using authentication logs.

Fix this in Active Backup For Microsoft 365 Scoped from the published advisory
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,300
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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-2025-4679 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
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