CVE-2017-15891
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 · uneditedImproper access control vulnerability in SYNO.Cal.EventBase in Synology Calendar before 2.0.1-0242 allows remote authenticated users to modify calendar event 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 confidenceImproper access control in Synology Calendar's SYNO.Cal.EventBase component allows authenticated users to modify calendar events they should not have permission to access. The vulnerability stems from insufficient authorization checks in the event modification functionality, enabling privilege escalation within the calendar application.
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< 2.0.1-0242CVSS 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
- None
- Integrity
- High
- Availability
- None
CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/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 checksWork through these to decide whether this CVE applies to you.
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Identify Synology Calendar installationLocate the Synology Calendar package in your Synology NAS package center or file system. This is typically managed through DSM's Package Manager.Affected if Synology Calendar is not installed on the Synology NAS environment.
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Determine installed version of Synology CalendarAccess the package information in Synology Package Center to view the current version number of Synology Calendar, or use the command line to query the installed package version if available.Affected if The installed version is lower than 2.0.1-0242 (e.g., 2.0.0-xxxx, 1.x.x, etc.).
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Verify SYNO.Cal.EventBase component is presentConfirm that the Synology Calendar web application is accessible and the SYNO.Cal.EventBase API component is available. This is typically found in the calendar web interface or API endpoints.Affected if The SYNO.Cal.EventBase component exists and is accessible through the calendar application.
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Check if calendar event modification is enabledLog into Synology Calendar as an authenticated user and verify that event creation and modification features are available. The vulnerability affects the event modification functionality.Affected if Calendar event modification functionality is accessible to authenticated users in the Synology Calendar application.
A Synology NAS environment is affected if Synology Calendar is installed with a version lower than 2.0.1-0242 and the calendar event modification feature is accessible to authenticated users.
Generated from the published advisory. Verify against your own configuration.
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 data2.0.1-0242
Upgrade Synology Calendar to version 2.0.1-0242 or later. If immediate patching is not possible, restrict network access to the calendar service and audit user permissions for calendar events.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2017-15891 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2017-15891 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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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