CVE-2021-29087
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 in webapi component in Synology DiskStation Manager (DSM) before 6.2.3-25426-3 allows remote attackers to 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 · high confidenceA path traversal vulnerability in the webapi component of Synology DiskStation Manager (DSM) versions prior to 6.2.3-25426-3 allows remote attackers to write arbitrary files to the filesystem via unspecified vectors. This can lead to remote code execution if attackers write malicious scripts to web-accessible directories.
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>= 6.2, < 6.2.3-25426-3< 3.1-23033CVSS 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/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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Check installed DSM versionLog into the Synology web interface and go to Control Panel > DSM Desktop > DSM version, or run `cat /etc/VERSION` via SSH on the deviceAffected if The version is 6.2.x but lower than 6.2.3-25426-3, or the version shows as any build before 3.1-23033 for Unified Controller systems
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Verify webapi endpoint is accessibleAttempt to reach the webapi endpoint at `https://[your-dsm-ip]/webapi/` from a network clientAffected if The endpoint responds with JSON data, indicating the webapi is exposed and reachable
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Inspect web-accessible directories for unauthorized filesCheck directories such as /webman/ and /webapi/ for any unexpected or recently created script files (e.g., .php, .cgi, .sh) using `ls -la /var/packages/WebStation/target/apache22/data/` or the equivalent web root pathAffected if Any unfamiliar script files exist that were not intentionally deployed by an administrator
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Review file creation timestamps in web directoriesUse `find /var/packages/WebStation/ -type f -mtime -30` (or similar) to list files modified within the last 30 days in web-accessible directoriesAffected if Files appear with creation/modification timestamps that correlate with the period when the vulnerability was publicly disclosed or actively exploited
A system is affected if it runs DSM version 6.2 through 6.2.3-25426-2 (or Unified Controller below 3.1-23033) AND has the webapi component network-accessible, with potential indicators being unauthorized script files in web directories.
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 data3.1-230336.2.3-25426-3
Upgrade Synology DSM to version 6.2.3-25426-3 or later to patch the path traversal vulnerability. If immediate patching is not possible, restrict network access to the webapi interface and monitor for unauthorized file creation.
- Consultation1.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-29087 — 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-2021-29087 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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