CVE-2015-2851
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 · uneditedclient_chown in the sync client in Synology Cloud Station 1.1-2291 through 3.1-3320 on OS X allows local users to change the ownership of arbitrary files, and consequently obtain root access, by specifying a filename.
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 confidenceThe client_chown function in Synology Cloud Station's sync client (versions 1.1-2291 through 3.1-3320 on OS X) allows local users to change ownership of arbitrary files by specifying any filename. This local privilege escalation vulnerability enables an unprivileged local user to take ownership of system files and obtain root access.
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= 1.1-2291= 2.0-2291= 2.0-2402= 2.1-2561= 2.1-2570= 2.1-2577= 3.0-3005= 3.0-3103= 3.0-3108= 3.0-3109= 3.0-3111= 3.1-3317CVSS 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
- Local
- Complexity
- Low
- Authentication
- Single
- Confidentiality
- Complete
- Integrity
- Complete
- Availability
- Complete
AV:L/AC:L/Au:S/C:C/I:C/A:C
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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Check if Synology Cloud Station is installedOpen Finder, go to /Applications folder, or run 'ls /Applications | grep -i cloud' in Terminal to list installed applications containing 'cloud' in the nameAffected if Synology Cloud Station or Cloud Station appears in the applications list
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Identify the installed versionRight-click the Cloud Station app in /Applications, select 'Get Info', or run 'defaults read /Applications/Synology\ Cloud\ Station.app/Contents/Info CFBundleVersion' in TerminalAffected if The displayed version matches or falls between 1.1-2291 and 3.1-3320 (including the specific versions: 1.1-2291, 2.0-2291, 2.0-2402, 2.1-2561, 2.1-2570, 2.1-2577, 3.0-3005, 3.0-3103, 3.0-3108, 3.0-3109, 3.1-3111, 3.1-3317)
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Verify the client is actively runningOpen Activity Monitor or run 'ps aux | grep -i cloud' in Terminal to see if the Cloud Station sync client process is currently activeAffected if The Cloud Station sync client process is running on the OS X system
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Confirm OS X platformCheck System Information or run 'uname -a' in Terminal to confirm the operating system is macOS / OS XAffected if The system is running OS X (this vulnerability affects only OS X versions of the client)
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Check for any active sync configurationsLook at the Cloud Station preferences or run 'ls ~/Library/Application\ Support/SynologyCloudStation/' to see if any sync tasks are configuredAffected if User sync folders are configured and the client is operational
The environment is affected if Synology Cloud Station version 1.1-2291 through 3.1-3320 is installed and running on OS X, allowing an unprivileged local user to exploit the client_chown function for privilege escalation.
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 dataApply vendor-supplied patches or update to a patched version of Synology Cloud Station. Until patched, monitor local user activity and restrict access to the Cloud Station client for untrusted users.
- Consultation2.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2015-2851 — 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-2015-2851 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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