CVE-2021-29086
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 · uneditedExposure of sensitive information to an unauthorized actor vulnerability in webapi component in Synology DiskStation Manager (DSM) before 6.2.3-25426-3 allows remote 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 confidenceA pre-authentication information disclosure vulnerability exists in the webapi component of Synology DiskStation Manager (DSM). Attackers can remotely obtain sensitive information without authentication by exploiting unspecified vectors in the web API. This affects all DSM versions prior to 6.2.3-25426-3.
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
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/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 checksWork through these to decide whether this CVE applies to you.
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Identify DSM versionLog into the Synology NAS via SSH or Control Panel, then check the version in Control Panel > Info Center > General, or run 'cat /etc/VERSION' via SSHAffected if version is 6.2.3-25426-3 or lower, or the installed version starts with 6.2 and is less than 6.2.3-25426-3, or for Unified Controller versions below 3.1-23033
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Confirm webapi component is accessibleAttempt to reach the webapi endpoint via HTTP/HTTPS, for example by accessing 'https://<your-nas-ip>/webapi/query.cgi?api=SYNO.API.Info&version=1&method=query' from a network-connected hostAffected if the webapi interface responds without requiring authentication, indicating the component is exposed
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Verify pre-authentication info disclosureSend an unauthenticated request to common webapi endpoints to confirm information can be retrieved without credentialsAffected if sensitive system information, configuration details, or API responses are returned without authentication being required
Your environment is affected if DSM version is below 6.2.3-25426-3 (or Unified Controller is below 3.1-23033) AND the webapi component is network-accessible without authentication.
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 DSM to version 6.2.3-25426-3 or later. If immediate patching is not feasible, consider restricting network access to the webapi interface via firewall rules or VPN access controls.
- Consultation3.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-29086 — 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-2021-29086 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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