CVE-2021-34808
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 · uneditedServer-Side Request Forgery (SSRF) vulnerability in cgi component in Synology Media Server before 1.8.3-2881 allows remote attackers to access intranet resources 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 confidenceServer-Side Request Forgery (SSRF) vulnerability in the cgi component of Synology Media Server allows remote attackers to make the server perform requests to intranet resources that should not be accessible from the outside. The vulnerability exists in versions prior to 1.8.3-2881 and enables attackers to potentially reach internal services, APIs, or infrastructure by tricking the Media Server into making arbitrary HTTP requests.
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< 1.8.3-2881CVSS 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
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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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Verify Media Server package is installedLog into Synology DSM, open Package Center, and look for 'Media Server' in the installed packages list. Alternatively, check via SSH by listing installed packages with 'sudo synopkg list --installed' or checking /var/packages/ for Media Server directory.Affected if Media Server package is not installed, the vulnerability does not apply
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Determine installed Media Server versionIn DSM Package Center, click on Media Server and view the version number displayed. Via SSH, run 'synopkg get MediaServer' or inspect the INFO file in /var/packages/MediaServer/Affected if Version is less than 1.8.3-2881, indicating the vulnerable version is installed
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Check if cgi component is accessibleThe cgi component is typically accessible at /webapi/mediaclient.cgi or similar endpoints. Attempt to access the Media Server CGI endpoint from an external system or verify via DSM > Application Portal > Reverse Proxy rules if the cgi interface is exposed.Affected if The cgi endpoint is externally accessible without authentication, the SSRF can be exploited
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Verify outbound network connectivity from NASCheck firewall rules in DSM > Security > Firewall to determine if the NAS can initiate outbound connections. Review if the Media Server has permission to make HTTP requests to arbitrary destinations.Affected if The NAS permits outbound HTTP connections from Media Server processes, an attacker could leverage the SSRF to reach internal resources
The environment is affected if Synology Media Server version is below 1.8.3-2881 AND the cgi component is accessible, allowing remote attackers to abuse the server's network position.
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 data1.8.3-2881
Upgrade Synology Media Server to version 1.8.3-2881 or later. If immediate patching is not feasible, implement network segmentation and firewall rules to restrict the Media Server's ability to make outbound connections to internal network ranges.
- Consultation2.0 h
- Implementation1.0 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-2021-34808 — 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-2021-34808 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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