CVE-2021-20038
Confirmed PUBLISHEDA Stack-based buffer overflow vulnerability in SMA100 Apache httpd server's mod_cgi module environment variables allows a remote unauthenticated...
Recommended Action
Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
At a Glance
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.
- CVE Published
- Dec 08, 2021
- Exploitation Reported
- Jan 28, 2022
- CVSS
- 9.8 Critical
- EPSS
- 99.9%
Affected Versions
| Vendor | Product | Version | Status |
|---|---|---|---|
| SonicWall |
SonicWall SMA100
|
10.2.0.8-37sv and earlier |
Affected |
| SonicWall |
SonicWall SMA100
|
10.2.1.1-19sv and earlier |
Affected |
| SonicWall |
SonicWall SMA100
|
10.2.1.2-24sv and earlier |
Affected |
CVE References
- psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0026 psirt.global.sonicwall.com · CVE Record https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0026
- GitHub — jbaines-r7/badblood github.com · CVE Record https://github.com/jbaines-r7/badblood
- rapid7.com/blog/post/2022/01/11/cve-2021-20038-42-sonic... rapid7.com · CVE Record https://www.rapid7.com/blog/post/2022/01/11/cve-2021-20038-42-sonicwa...
Recommended Actions
- Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
- Check enrichment artifacts for scanner coverage and available PoCs before rolling remediation validation.
- Use the Pro API to automate enrichment, telemetry, and workflow delivery for VM, SOC, and CTI pipelines.
Known Exploited Vulnerability Sources
Catalogues that list this CVE as a known exploited vulnerability.
Per-source evidence links for KEV attestations are available through the KEVIntel Pro API.
Learn about Pro API access| Source | Added |
|---|---|
| CISA First | 2022-01-28 00:00 UTC |
| Tenable Blog | 2026-07-15 17:14 UTC |
Scanner Artifacts
Nuclei and Metasploit references linked to this CVE.
| Scanner | Reference | Detected |
|---|---|---|
| Nuclei | https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-20038.yaml | Apr 25, 2025 |
Virtual Patch
Compensating WAF rules to help reduce exposure to this CVE. Rule content and deployable vendor exports are available with KEVIntel Enterprise.
KEVIntel does not currently have a virtual patch for this CVE. When available, KEVIntel virtual patches ship as deployable ModSecurity, Cloudflare, and AWS WAF rules.
Enterprise feature. Virtual patch rule content and deployable vendor exports (ModSecurity, Cloudflare, AWS WAF) are available to KEVIntel Enterprise users.
CVSS Scores
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
AV:N/AC:L/Au:N/C:P/I:P/A:P
Exploitation Status
Exploited in the wild
Recorded 2022-01-28 00:00:00 UTC · CISA
Used in malware
Recorded 2022-01-28 00:00:00 UTC · CISA
Proof of concept available
Recorded 2022-08-08 03:38:06 UTC · GitHub
Scanner Integrations
| Scanner | Reference | Detected |
|---|---|---|
| Nuclei | https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-20038.yaml | Apr 25, 2025 |
Recent Mentions
Tenable Blog · Jul 15, 2026
SonicWall patched two recently exploited zero-day vulnerabilities in its SMA 1000 Series secure remote access appliances which may have been chained for unauthenticated remote code execution.Key takeawaysCVE-2026-15409 and CVE-2026-15410 are a pair of exploited vulnerabilities that may have been chained together to allow for code execution on SonicWall SMA1000 series appliances. Zero-day exploitation of these vulnerabilities has been observed and confirmed by SonicWall. Patches and indicators of compromise are available and urgent patching is recommended.BackgroundSonicWall's Secure Mobile Access (SMA) 1000 Series appliances are enterprise-grade SSL VPN gateways which serve as the front door to organizational networks. The SMA series models sit at the edge of the network, internet-facing by design. Because SMA 1000 appliances aggregate remote access credentials and sit directly on the internet, they represent high-value targets for attackers. A compromise at the appliance level can yield administrator credentials, VPN session tokens, and detailed knowledge of the internal network architecture sitting behind the gateway.On July 14, SonicWall disclosed two vulnerabilities that are being exploited together in the wild:CVEDescriptionCVSSv3CVE-2026-15409SonicWall SMA 1000 server-side request forgery (SSRF) vulnerability10CVE-2026-15410SonicWall SMA 1000 remote code execution vulnerability (RCE)7.2While the advisory does not specify if they were exploited in tandem, together they form a fully remote, unauthenticated path to arbitrary OS command execution on affected appliances.AnalysisCVE-2026-15409 is a SSRF vulnerability affecting the SMA 1000 Workplace interface. This flaw allows a remote, unauthenticated attacker to make network requests to locations of the attacker's choosing. In practice, SSRF on an internet-facing appliance can serve as a pivot, allowing an attacker to probe internal services, relay authentication material, or reach the AMC in a way that...
Potential Proof of Concepts
These PoCs are unverified and could contain malware. Use at your own risk.
github · Created 2022-08-08 03:38:06 UTC · 1 stars
nuclei · Created Unknown
Timeline
Key exploitation, disclosure, scanner coverage, and KEV attestation events for this CVE.
-
17:14 UTC 8 days ago17:14 UTC · 8 days ago
KEV confirmed by Tenable Blog
Exploitation attested by an external source
-
00:00 UTC about 1 year ago00:00 UTC · about 1 year ago
Nuclei template available
Scanner coverage available
-
03:38 UTC almost 4 years ago03:38 UTC · almost 4 years ago
Public PoC available
Public proof-of-concept code published
-
00:00 UTC over 4 years ago00:00 UTC · over 4 years ago
Added to CISA KEV
Listed in the CISA Known Exploited Vulnerabilities catalog
-
00:00 UTC over 4 years ago00:00 UTC · over 4 years ago
First public exploitation report
Exploit observed in malware
-
09:55 UTC over 4 years ago09:55 UTC · over 4 years ago
CVE published
Vulnerability disclosed publicly
-
00:00 UTC over 5 years ago00:00 UTC · over 5 years ago
CVE ID reserved
Identifier reserved by the CNA
Automate This Intelligence with the Pro API
Confidence scoring, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
Pro API Example
GET /api/v2/pro/kevs/CVE-2021-20038
{
"cve_id": "CVE-2021-20038",
"title": "A Stack-based buffer overflow vulnerability in SMA100 Apache httpd server\'s m...",
"affected_vendor": "SonicWall",
"affected_product": "SonicWall SMA100",
"affected_versions": [
{ "vendor": "...", "product": "...", "status": "affected", "display_label": "..." }
],
"confidence": "Confirmed",
"cvss_score": 9.8,
"epss_score": 0.99912,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "...": "Pro API fields" },
"proof_of_concepts": [ "..." ],
"scanner_integrations": [ "..." ]
}