DockerApplication · Synology
CVE-2021-33183
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 limitation of a pathname to a restricted directory ('Path Traversal') vulnerability container volume management component in Synology Docker before 18.09.0-0515 allows local users to read or write arbitrary files 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 confidenceA path traversal vulnerability exists in the container volume management component of Synology Docker versions prior to 18.09.0-0515. The improper limitation of pathnames allows local users to read or write arbitrary files on the host system by manipulating container volume paths, potentially escaping container isolation boundaries.
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
DockerApplication
< 18.09.0-0515CVSS 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
- Privileges
- High
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/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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Check Synology Docker package versionOpen Synology DSM Package Center, locate the Docker package, and note the installed version number. Alternatively, run 'sudo synopkg list --name Docker' or check via SSH with 'docker --version' to confirm the Docker version.Affected if The installed version is lower than 18.09.0-0515
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Verify Docker service is activeIn DSM, go to Control Panel > Terminal & SNMP > Terminal and enable SSH access if needed, then connect via SSH and run 'sudo docker info' or check the Docker service status in Package Center.Affected if Docker service is running and the version check shows it is vulnerable
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Identify containers with volume mountsRun 'sudo docker ps -a --format "{{.Names}}: {{.Mounts}}"' via SSH to list all containers and their mounted volumes. Review the volume bindings for any custom host paths.Affected if Containers with volume mounts exist and the Docker version is below 18.09.0-0515, the path traversal could be exploited
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Inspect volume mount configuration filesCheck Docker configuration files such as /var/packages/Docker/etc/dockerd.json or container-specific config files in /var/packages/Docker/var/docker/containers/ for volume definitions.Affected if Volume mounts with relative paths or paths that could be manipulated are present on a vulnerable version
A user is affected if Synology Docker version is below 18.09.0-0515 and the system is used to run containers with volume mounts, allowing potential path traversal escapes.
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 data18.09.0-0515
Upgrade Synology Docker to version 18.09.0-0515 or later. If immediate patching is not feasible, restrict local user access to the Docker service and monitor for suspicious volume mount operations.
Fix this in Docker
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-33183 — 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-2021-33183 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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- Version or environment caveats, and links to real fixes
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