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Weekly Signal
Live intelligence Updated 19 Aug 2026 · 12:58 UTC

Sonicwall · SMA 100 Appliances, Sma 200 Firmware, Sma 210 Firmware +3 more

CVE-2021-20038

SonicWall SMA 100 Appliances Stack-Based Buffer Overflow Vulnerability

Recommended action

Treat this as an immediate remediation priority. Apply updates per vendor instructions.

View response plan
CVSS9.8
EPSS99.9%
KEVYes
ExploitationConfirmed exploitation
PatchPatch or guidance available ↓

Assessment

Why it matters

CISA lists this vulnerability as known to be exploited; exploitation is confirmed; EPSS is 99.9%; technical severity is CVSS 9.8.

A Stack-based buffer overflow vulnerability in SMA100 Apache httpd server's mod_cgi module environment variables allows a remote unauthenticated attacker to potentially execute code as a 'nobody' user in the appliance. This vulnerability affected SMA 200, 210, 400, 410 and 500v appliances firmware 10.2.0.8-37sv, 10.2.1.1-19sv, 10.2.1.2-24sv and earlier versions.

Who should care

  • Teams operating SMA 100 Appliances, Sma 200 Firmware, Sma 210 Firmware +3 more
  • Vulnerability and exposure management teams
  • Security operations teams monitoring exploitation activity

Response plan

What I would do

  1. Confirm whether SMA 100 Appliances, Sma 200 Firmware, Sma 210 Firmware +3 more is present in the environment.
  2. Identify affected versions and establish whether vulnerable services are exposed or reachable.
  3. Apply updates per vendor instructions.
  4. Review relevant security telemetry for evidence of attempted or successful exploitation.
  5. Document the remediation decision and track it to verified completion.

Vendor remediation

Patch and remediation links

Use the vendor source below to confirm the correct fixed version, package or mitigation for your affected product.

Technical details

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE
CWE-121
Affected versions
Sonicwall SMA 100 Appliances; Sonicwall Sma 200 Firmware (Version: 10.2.1.2-24sv); Sonicwall Sma 210 Firmware (Version: 10.2.1.2-24sv); Sonicwall Sma 400 Firmware (Version: 10.2.1.2-24sv); Sonicwall Sma 410 Firmware (Version: 10.2.1.2-24sv); Sonicwall Sma 500v Firmware (Version: 10.2.1.2-24sv)
Published
8 December 2021
Attack vector
Network
Privileges required
None
User interaction
None

Signal timeline

  1. CVE published
  2. Added to CISA KEV
  3. Latest EPSS score: 99.9%
  4. Signal calculated at 88

External references

Live public intelligence This assessment combines public-source evidence. Validate the affected product, version and exposure against your own environment before making a risk decision.