CVE-2021-20042
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 · uneditedAn unauthenticated remote attacker can use SMA 100 as an unintended proxy or intermediary undetectable proxy to bypass firewall rules. This vulnerability affected SMA 200, 210, 400, 410 and 500v appliances.
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 confidenceThe SMA 100 series appliances (SMA 200, 210, 400, 410, 500v) contain an unauthenticated proxy vulnerability allowing remote attackers to use the appliance as an undetectable intermediary to bypass firewall rules and route malicious traffic through the compromised device.
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= 9.0.0.11-31sv= 10.2.0.8-37sv= 10.2.1.1-19sv= 9.0.0.11-31sv= 10.2.0.8-37sv= 10.2.1.1-19sv= 9.0.0.11-31sv= 10.2.0.8-37sv= 10.2.1.1-19sv= 9.0.0.11-31sv= 10.2.0.8-37sv= 10.2.1.1-19sv= 9.0.0.11-31sv= 10.2.0.8-37sv= 10.2.1.1-19svCVSS 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
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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 the SMA appliance modelAccess the SMA web interface or run 'get system status' via CLI to confirm the model number is one of: SMA 200, SMA 210, SMA 400, SMA 410, or SMA 500vAffected if Model is any of SMA 200, 210, 400, 410, or 500v
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Check the installed firmware versionNavigate to System > Status or run 'get system status' in CLI to retrieve the firmware version. Compare against these affected versions: 9.0.0.11-31sv, 10.2.0.8-37sv, or 10.2.1.1-19svAffected if Firmware version exactly matches 9.0.0.11-31sv, 10.2.0.8-37sv, or 10.2.1.1-19sv
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Test for unauthenticated proxy accessSend an HTTP request through the SMA appliance to an external destination without providing any authentication (for example, use the SMA as an HTTP proxy to connect to an external IP). Observe if the request is proxied successfully without loginAffected if The SMA appliance successfully proxies the request without requiring authentication
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Review proxy access logsCheck the SMA logs under Reporting > Logs or run 'get log' for entries showing unauthenticated proxy connections from external IPsAffected if Logs show proxy requests from unauthenticated external sources
If the device is an SMA 200/210/400/410/500v running firmware version 9.0.0.11-31sv, 10.2.0.8-37sv, or 10.2.1.1-19sv AND the appliance can be used as an unauthenticated proxy to reach external hosts, the environment is affected by CVE-2021-20042.
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 dataImmediately apply the vendor firmware update to all affected SMA appliances and implement additional network segmentation or access controls to prevent unauthorized proxy usage.
- Consultation4.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20042 — 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-2021-20042 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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