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Sma 200 FirmwareOperating system · Sonicwall

CVE-2021-20041

HIGH · 7.5 CVSS v3.1 Published 2021-12-08
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

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 · unedited
An unauthenticated and remote adversary can consume all of the device's CPU due to crafted HTTP requests sent to SMA100 /fileshare/sonicfiles/sonicfiles resulting in a loop with unreachable exit condition. 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 · high confidence

A denial of service vulnerability in SonicWall SMA 200, 210, 400, 410, and 500v appliances allows unauthenticated remote attackers to send crafted HTTP requests to /fileshare/sonicfiles/sonicfiles, triggering an infinite loop with unreachable exit condition that consumes all CPU resources.

MitigationApply vendor-provided patches or firmware updates for affected SMA appliances; consider network-level rate limiting or blocking of the vulnerable endpoint as a temporary mitigation.

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
Sma 200 FirmwareOperating system
Affected:= 9.0.0.11-31sv= 10.2.0.8-37sv= 10.2.1.1-19sv
Sma 210 FirmwareOperating system
Affected:= 9.0.0.11-31sv= 10.2.0.8-37sv= 10.2.1.1-19sv
Sma 410 FirmwareOperating system
Affected:= 9.0.0.11-31sv= 10.2.0.8-37sv= 10.2.1.1-19sv
Sma 400 FirmwareOperating system
Affected:= 9.0.0.11-31sv= 10.2.0.8-37sv= 10.2.1.1-19sv
Sma 500v FirmwareOperating system
Affected:= 9.0.0.11-31sv= 10.2.0.8-37sv= 10.2.1.1-19sv

CVSS 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
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify SMA appliance model
    Access the SonicWall SMA web management console and locate the Appliance Status or System Information page, or run 'get system status' via CLI to confirm the model is SMA 200, 210, 400, 410, or 500v
    Affected if the model is one of SMA 200, 210, 400, 410, or 500v and the firmware matches affected versions
  2. Check installed firmware version
    In the SMA web interface, go to System > Status or navigate to the Firmware/Upgrade section. Alternatively, run 'show version' or 'get system info' via CLI to retrieve the exact firmware version string
    Affected if the firmware version equals 9.0.0.11-31sv, 10.2.0.8-37sv, or 10.2.1.1-19sv
  3. Verify vulnerable endpoint is accessible
    From an external host, attempt a curl or HTTP request to the path /fileshare/sonicfiles/sonicfiles on the SMA appliance (e.g., curl -k https://<SMA-IP>/fileshare/sonicfiles/sonicfiles)
    Affected if the endpoint responds with any HTTP status code (even an error or redirect), indicating the file sharing feature is enabled and reachable
  4. Check for CPU exhaustion symptoms
    Log into the SMA CLI and run 'top' or 'show processes cpu' to review CPU utilization, or access the web interface System > Status page to observe if CPU usage is at or near 100%
    Affected if CPU usage is sustained at 100% or processes show the /fileshare/sonicfiles/sonicfiles handler consuming all available CPU cycles

The environment is affected if the appliance is an SMA 200, 210, 400, 410, or 500v running firmware version 9.0.0.11-31sv, 10.2.0.8-37sv, or 10.2.1.1-19sv, and the /fileshare/sonicfiles/sonicfiles endpoint is exposed and responding.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply vendor-provided patches or firmware updates for affected SMA appliances; consider network-level rate limiting or blocking of the vulnerable endpoint as a temporary mitigation.

Fix this in Sma 200 Firmware Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA3.0 h
27.0 hours of engineering $4,800
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-20041 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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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