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Sma 100 FirmwareOperating system · Sonicwall

CVE-2021-20049

HIGH · 7.5 CVSS v3.1 Published 2021-12-23
Fix available
A fix is available. Upgrade to 10.0.0.0 or later.
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 vulnerability in SonicWall SMA100 password change API allows a remote unauthenticated attacker to perform SMA100 username enumeration based on the server responses. This vulnerability impacts 10.2.1.2-24sv, 10.2.0.8-37sv and earlier 10.x versions.

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

The vulnerability exists in the SonicWall SMA100 series SSL VPN password change API. An unauthenticated remote attacker can send specially crafted requests to the API endpoint and observe differential server responses to enumerate valid usernames. This username enumeration can then be used as a stepping stone for brute-force attacks or credential stuffing against the VPN portal.

MitigationApply the vendor-supplied patch or update to a fixed SonicWall SMA100 firmware version. If immediate patching is not feasible, monitor authentication logs for anomalous password change API access patterns and consider restricting access to the password change interface via 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 100 FirmwareOperating system
Affected:< 10.0.0.0= 10.2.0.8-37sv= 10.2.1.2-24sv
Sma 200 FirmwareOperating system
Affected:< 10.0.0.0= 10.2.0.8-37sv= 10.2.1.2-24sv
Sma 210 FirmwareOperating system
Affected:< 10.0.0.0= 10.2.0.8-37sv= 10.2.1.2-24sv
Sma 400 FirmwareOperating system
Affected:< 10.0.0.0= 10.2.0.8-37sv= 10.2.1.2-24sv
Sma 410 FirmwareOperating system
Affected:< 10.0.0.0= 10.2.0.8-37sv= 10.2.1.2-24sv
Sma 500v FirmwareOperating system
Affected:< 10.0.0.0= 10.2.0.8-37sv= 10.2.1.2-24sv

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
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 checks

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

  1. Identify the SMA device firmware version
    Access the SMA web interface under 'System Administration > Firmware' or use the command 'show version' via SSH console to retrieve the currently running firmware version
    Affected if The installed version is < 10.0.0.0, or exactly 10.2.0.8-37sv, or exactly 10.2.1.2-24sv
  2. Confirm the password change API endpoint is accessible
    Attempt to reach the password change API endpoint (typically /api/sonicwall-login/change_password or similar paths under /api/) from an unauthenticated network perspective
    Affected if The API endpoint responds to unauthenticated requests without requiring login credentials
  3. Test for username enumeration via differential responses
    Send password change API requests with valid usernames and invalid usernames, then compare HTTP response codes, response times, or error message content between them
    Affected if The server returns measurably different responses for valid usernames versus invalid usernames
  4. Review authentication logs for enumeration patterns
    Examine SMA authentication logs (available via 'Log > Authentication' in the web UI or via syslog) for repeated password change API calls with different username values in a short timeframe
    Affected if Logs show repeated password change API requests from unauthenticated sources or patterns indicative of username probing

A defender is affected if the SMA device runs a firmware version within the listed ranges AND the password change API permits unauthenticated access that yields distinguishable responses for valid versus invalid usernames.

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.

dbcve · scoped
Upgrade available Upgrade to 10.0.0.0 or later
Fixed in 10.0.0.0
Interim mitigation

Apply the vendor-supplied patch or update to a fixed SonicWall SMA100 firmware version. If immediate patching is not feasible, monitor authentication logs for anomalous password change API access patterns and consider restricting access to the password change interface via firewall rules.

Recommended fix Moderate confidence

Latest available SMA 100 series firmware (10.2.1.x or higher stable release from SonicWall)

  1. 1. Identify the current firmware version of the affected SMA device by accessing the management interface or using the command line interface.
  2. 2. Access the SonicWall support portal at psirt.global.sonicwall.com to obtain the latest firmware version for your specific SMA model (100, 200, 210, 400, 410, or 500v).
  3. 3. Download the latest stable firmware release from the SonicWall support portal.
  4. 4. Backup the current device configuration through the web management interface under System > Settings > Backup/Restore.
  5. 5. Upload and install the new firmware through the device's firmware update functionality (typically found under System > Settings > Firmware Update).
  6. 6. After installation, verify the device is operational and confirm the new firmware version is applied.
  7. 7. Test that the password change API no longer reveals username existence through differential server responses.
Caveat Review SonicWall release notes for any configuration or feature changes between current and new firmware versions before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Sma 100 Firmware Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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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-2021-20049 in production — separate from our analysis above.

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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
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  • No spam, self-promotion, credentials, or personal data