Cyber Resilience

CVE-2021-20038

Memory Safety in Sonicwall Sma 200 Firmware 10.2.0.8-37sv … 10.2.1.2-24sv

CISA KEVActive ExploitationEUVD ExploitedPublic PoCRansomware-linkedMemory Safety
Published
08 December 2021
Modified
31 October 2025
KEV Added
28 January 2022
Patch / advisory
View advisory
CVSS Score v3.1 9.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.99 100.0th percentile
Risk Priority 97 floored blend · peak EPSS

Summary

CVE-2021-20038 is a critical-severity Stack-based Buffer Overflow (CWE-121) vulnerability in Sonicwall Sma 200 Firmware. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 0.0% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

A stack-based buffer overflow vulnerability exists in the mod_cgi module of the Apache httpd server on SMA100 appliances, triggered via environment variables. It affects SonicWall SMA 200, 210, 400, 410, and 500v appliances running firmware 10.2.0.8-37sv, 10.2.1.1-19sv, 10.2.1.2-24sv, and earlier versions, and is also associated with CWE-121 and CWE-787.

A remote unauthenticated attacker can exploit the flaw over the network to potentially execute arbitrary code as the 'nobody' user on the appliance. The issue received a CVSS 3.1 score of 9.8, reflecting the combination of low attack complexity, no required privileges or user interaction, and full impact on confidentiality, integrity, and availability.

SonicWall PSIRT advisory SNWLID-2021-0026 and related reporting from Rapid7 document the issue, while public proof-of-concept code is available in the badblood repository.

EU & UK References

Vulnerability Data

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…

more

appliances firmware 10.2.0.8-37sv, 10.2.1.1-19sv, 10.2.1.2-24sv and earlier versions.

CWE(s)
CWE-121CWE-787
KEV Date Added
28 January 2022

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1211 Exploitation for Stealth Stealth
Adversaries may exploit vulnerabilities to evade detection by hiding activity, suppressing logging, or operating within trusted or unmonitored components.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2024-45318Same product: Sonicwall Sma 200
CVE-2024-53703Same product: Sonicwall Sma 200
CVE-2025-40596Same product: Sonicwall Sma 210
CVE-2023-41712Same vendor: Sonicwall
CVE-2023-39276Same vendor: Sonicwall
CVE-2023-39279Same vendor: Sonicwall
CVE-2023-39277Same vendor: Sonicwall
CVE-2023-6340Same vendor: Sonicwall
CVE-2024-29012Same vendor: Sonicwall
CVE-2022-22274Same vendor: Sonicwall

Affected Assets

sonicwall
sma 200 firmware
10.2.0.8-37sv, 10.2.1.1-19sv, 10.2.1.2-24sv
sonicwall
sma 210 firmware
10.2.0.8-37sv, 10.2.1.1-19sv, 10.2.1.2-24sv
sonicwall
sma 410 firmware
10.2.0.8-37sv, 10.2.1.1-19sv, 10.2.1.2-24sv
sonicwall
sma 400 firmware
10.2.0.8-37sv, 10.2.1.1-19sv, 10.2.1.2-24sv
sonicwall
sma 500v firmware
10.2.0.8-37sv, 10.2.1.1-19sv, 10.2.1.2-24sv

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 2 hardening rules · 2 OS baselines
Validate
Prove the fix (OWASP ASVS)

—

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SI-16 Memory Protection
addresses: CWE-787

Out-of-bounds writes that corrupt control flow or inject shellcode are rendered non-executable by the same memory protections.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure-development practices directly prevent introduction of stack buffer overflows.

ID.RA-01 partial match
prevents

Vulnerability scanning can discover stack buffer overflows but does not prevent their introduction.

PR.PS-02 partial match
prevents

Patching eliminates known instances of the weakness after discovery.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing (fuzzing, static analysis) detects stack overflows before release.

A.8.25 Secure development life cycle partial match
prevents

Secure SDLC mandates buffer-safety practices that directly prevent stack overflows.

A.8.26 Application security requirements partial match
prevents

Application security requirements can specify buffer-size and input-validation rules.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles include memory-safety and least-privilege stack usage.

A.8.28 Secure coding partial match
prevents

Secure coding standards explicitly forbid unsafe buffer handling that causes CWE-121.

A.8.32 Change management partial match
prevents

Change management can enforce review gates that catch unsafe memory operations before deployment.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).

Oracle Linux 8 (1 rule)
  • V-248594 OL 8 must implement address space layout randomization (ASLR) to protect its memory from unauthorized code execution. prevents CWE-121
Oracle Linux 9 (1 rule)
  • V-271452 OL 9 must use a Linux Security Module configured to enforce limits on system services. prevents CWE-121

References