Is CVE-2021-20038 in the CISA KEV catalog?

Yes. CVE-2021-20038 is on the CISA Known Exploited Vulnerabilities list, added 2022-01-28, and has known ransomware campaign use.

What is the CVSS severity of CVE-2021-20038?

CVE-2021-20038 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2021-20038?

CVE-2021-20038 has an EPSS score of 99.91% (100th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix or mitigate CVE-2021-20038?

No published fix for CVE-2021-20038 has been found yet. It is on the CISA Known Exploited Vulnerabilities list; federal agencies must remediate by 2022-02-11. Apply the vendor's mitigations per CISA's guidance.

CVE & CISA-KEV Catalog

CVE-2021-20038

CRITICALCISA KEVEPSS 100th pctl

9.8

CVSS v3

NVD

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.

CWE-121Stack-based Buffer Overflow CWE-787Out-of-bounds Write

How to fix

Actively exploited, no published fix found yet

CISA required action: Apply updates per vendor instructions.

Federal remediation due: 2022-02-11

Known ransomware campaign use

Mitigation guidance may be in the linked vendor advisories in the References section below.

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CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

99.91%probability of exploitation in 30 days

100thpercentile

Very high risk: more likely to be exploited than 100% of all known CVEs.

Known Exploited Vulnerability (CISA KEV)

SonicWall SMA 100 Appliances Stack-Based Buffer Overflow Vulnerability

SonicWall SMA 100 devies are vulnerable to an unauthenticated stack-based buffer overflow vulnerability where exploitation can result in code execution.

Apply updates per vendor instructions.

Remediation due: 2022-02-11

Associated with ransomware campaigns

References

Exploit2

Vendor Advisory1

psirt.global.sonicwall.com

Government Resource1

cisa.gov

Related Vulnerabilities

Other CWE-121 (Stack-based Buffer Overflow) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-22457	Critical	9.0	100%	KEV + Ransom	Fix
CVE-2025-0282	Critical	9.0	100%	KEV + Ransom	-
CVE-2009-0927	High	8.8	97%	KEV	Fix
CVE-2020-10924	High	8.8	87%	-	-
CVE-2022-20705	Critical	10.0	80%	-	-
CVE-2016-6563	Critical	9.8	80%	-	-

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-10-31.