CVE-2021-20038: SonicWall SMA 100 Appliances Stack-Based Buffer Overflow Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 28 Jan 2022, 51 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 99.9%
EPSS score, percentile 100 of all scored records
- How severe?
- 9.8 Critical
CVSS v3.1 base score, from CISA's enrichment of the record
- What should I do?
CISA deadline 11 Feb 2022. Apply updates per vendor instructions.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- 10.2.0.8-37sv and earlier
- 10.2.1.1-19sv and earlier
- 10.2.1.2-24sv and earlier
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
What to do
Required action, set by CISA
Apply updates per vendor instructions.
CISA due date for this action: 11 February 2022.
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | 10.2.0.8-37sv and earlier |
| Affected | 10.2.1.1-19sv and earlier |
| Affected | 10.2.1.2-24sv and earlier |
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
About this vulnerability
SonicWall SMA 100 devies are vulnerable to an unauthenticated stack-based buffer overflow vulnerability where exploitation can result in code execution.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2021-20038 to its Known Exploited Vulnerabilities (KEV) catalog on 28 Jan 2022.
- CISA marks it as known to be used in ransomware campaigns.
- The due date CISA sets for the required action is 11 Feb 2022.
- The CVE record was published on 8 Dec 2021, 51 days before it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 9.8 (Critical), taken from CISA's enrichment of the record.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 99.9% (percentile 100), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact total.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.
Description
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.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
Weakness
- CWE-121: Stack-based Buffer Overflow
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| 8 Dec 2021 | CVE record published |
| 28 Jan 2022 | Added to CISA KEV |
| 11 Feb 2022 | CISA due date for the required action |
| 21 Oct 2025 | CVE record last updated |
References
More exploited SonicWall vulnerabilities
- CVE-2026-83548: SonicWall SMA1000 Appliances Server-Side Request Forgery Vulnerability
- CVE-2026-83549: SonicWall SMA1000 Appliances OS Command Injection Vulnerability
- CVE-2026-15409: SonicWall SMA1000 Appliances Server-Side Request Forgery Vulnerability
- CVE-2026-15410: SonicWall SMA1000 Appliances Code Injection Vulnerability
- CVE-2025-40602: SonicWall SMA1000 Missing Authorization Vulnerability
- CVE-2023-44221: SonicWall SMA100 Appliances OS Command Injection Vulnerability