dbcve.org
Sma 200 FirmwareOperating system · Sonicwall

CVE-2021-20040

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
A relative path traversal vulnerability in the SMA100 upload funtion allows a remote unauthenticated attacker to upload crafted web pages or files as a 'nobody' user. 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 relative path traversal vulnerability exists in the SMA100 series appliances' file upload function, allowing remote unauthenticated attackers to bypass path validation and upload arbitrary files to arbitrary locations on the system. The uploaded files are created with 'nobody' user privileges, which could enable web shell deployment or further privilege escalation.

MitigationApply vendor patches for SMA 200, 210, 400, 410, and 500v appliances; if patches unavailable, restrict external access to the SMA management interface via network segmentation or firewall rules.

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

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

  1. Identify SMA appliance model
    Access the SMA device web interface or use the command line interface (CLI) to retrieve the hardware model number. Look for SMA 200, SMA 210, SMA 400, SMA 410, or SMA 500v designations in the system information or device status page.
    Affected if The model is one of: SMA 200, SMA 210, SMA 400, SMA 410, or SMA 500v.
  2. Retrieve firmware version
    In the SMA web interface, navigate to System > Status or Device > About to view the installed firmware version. Alternatively, use the CLI command 'sysctl -a' or check '/etc/version' via SSH to obtain the exact firmware build number.
    Affected if The firmware version matches exactly 10.2.0.8-37sv or 10.2.1.1-19sv.
  3. Verify management interface accessibility
    Determine if the SMA web management interface (typically ports 443 or 8443) is accessible from untrusted networks. Review firewall rules, VPN policies, and network segmentation configurations to confirm whether the interface is exposed to the internet or untrusted internal segments.
    Affected if The SMA management interface is reachable from untrusted network segments or the public internet without proper access controls.
  4. Inspect for files owned by nobody user
    Access the SMA device via SSH and use 'find / -user nobody -type f 2>/dev/null' to list files created by the 'nobody' user. Check directories such as /var/www/html, /tmp, and user-upload directories for unexpected files.
    Affected if Unexpected files or scripts (especially .php, .sh, or executable files) exist on the system and are owned by the 'nobody' user.
  5. Review web root for suspicious scripts
    Examine the web document root directories (/var/www/html, /www, or similar) for unfamiliar PHP files, web shells, or uploaded artifacts. Use 'ls -la' to list files and check modification timestamps around the time of potential exploitation.
    Affected if Unknown PHP files, web shells, or scripts appear in web-accessible directories, particularly with recent creation or modification dates.

A defender is affected if they operate a SMA 200, 210, 400, 410, or 500v appliance running firmware version 10.2.0.8-37sv or 10.2.1.1-19sv, with the management interface accessible to untrusted networks, and unauthorized files owned by 'nobody' exist on the system.

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 patches for SMA 200, 210, 400, 410, and 500v appliances; if patches unavailable, restrict external access to the SMA management interface via network segmentation or firewall rules.

Fix this in Sma 200 Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,480
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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-2021-20040 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
  • No spam, self-promotion, credentials, or personal data