CVE Intelligence
CISA KEV Critical Memory corruption exploit reference

CVE-2021-20038 — SonicWall SMA 100 Appliances Stack-Based Buffer Overflow Vulnerability

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.

Published Dec 8, 2021 · Updated Oct 13, 2026 · Sources: CISA Known Exploited Vulnerabilities, NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: sonicwall

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

CISA KEV · Jan 28, 2022 R used by ransomware (CISA) Detection templates (Nuclei) · 1Proofs of concept on GitHub · 3
How the score was calculated
  • Confirmed exploitation (CISA KEV)+35
  • Used in ransomware campaigns (CISA)+10
  • Public exploit/PoC (nuclei, github)+10
  • EPSS 99.9% (30-day exploitation probability)+15
  • Technical severity (critical)+10
  • Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Confirmed
CISA KEV, listed Jan 28, 2022
EPSS FIRST
99.91%
ahead of 100% of scored CVEs · Oct 14, 2026
Affects
Sonicwall
Sma 200 Firmware and 5 more
CVSS base
9.8
Critical · 4 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
Active
none · proof-of-concept · active
Automatable
Yes
can an attacker script the kill-chain steps
Technical impact
Total
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

CISA required action CISA

Apply updates per vendor instructions.

US federal deadline: Feb 11, 2022 — passed 1707 day(s) ago

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Sonicwall Sma 200 Firmware, Sonicwall Sma 210 Firmware, Sonicwall Sma 400 Firmware…).
  2. Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
  3. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  4. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  5. EPSS ahead of 100% of scored CVEs: prioritize it in the patch queue.
  6. Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Sonicwall Sma 200 Firmware version 10.2.1.1-19svversion 10.2.1.2-24svversion 10.2.0.8-37sv Vulnerable NIST National Vulnerability Database
Sonicwall Sma 210 Firmware version 10.2.0.8-37svversion 10.2.1.1-19svversion 10.2.1.2-24sv Vulnerable NIST National Vulnerability Database
Sonicwall Sma 400 Firmware version 10.2.0.8-37svversion 10.2.1.1-19svversion 10.2.1.2-24sv Vulnerable NIST National Vulnerability Database
Sonicwall Sma 410 Firmware version 10.2.0.8-37svversion 10.2.1.2-24svversion 10.2.1.1-19sv Vulnerable NIST National Vulnerability Database
Sonicwall Sma 500v Firmware version 10.2.0.8-37svversion 10.2.1.1-19svversion 10.2.1.2-24sv Vulnerable NIST National Vulnerability Database
Sonicwall SMA100 version 10.2.0.8-37sv and earlierversion 10.2.1.1-19sv and earlierversion 10.2.1.2-24sv and earlier Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
9.8 CVSS 3.1 Critical 3.9 5.9 nvd@nist.gov via NIST National Vulnerability Database
9.8 CVSS 3.1 Critical 3.9 5.9 134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database
9.8 CVSS 3.1 Critical — — GitHub, Inc. via GitHub Security Advisories
9.8 CVSS 3.1 Critical — — CISA-ADP via CVE Program (cve.org) e CISA ADP
7.5 CVSS 2.0 High 10.0 6.4 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-121 · Stack-based Buffer Overflow

Other CVEs with this weakness →

CISA KEV details CISA

CISA lists a CVE once it has evidence of exploitation against real targets.

Listed
Jan 28, 2022
Federal deadline
Feb 11, 2022
passed 1707 day(s) ago
Ransomware use
Known

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a reference date.

Public exploits, PoCs and detection templates

Public code that demonstrates or tests the flaw raises the odds of mass exploitation — and Nuclei templates help find vulnerable assets in your environment.

Detection templates (Nuclei)
Proofs of concept on GitHub

Warning: public PoCs are sometimes disguised malware. Use them only for authorized testing in an isolated environment. This portal does not host exploit code — it only points to the sources.

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 99.91%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
  • Hunt retroactively in logs from before Jan 28, 2022 (KEV listing): exploitation may have started earlier.
web/proxy/WAF logsnetwork IDS/IPSendpoint telemetry (EDR)crash dumps

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · sonicwall/sonicwall sma100
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Affected products added · sonicwall/sma 200 firmware, sonicwall/sma 210 firmware, sonicwall/sma 410 firmware, sonicwall/sma 400 firmware, sonicwal
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 9.8
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 13, 2026 · NIST National Vulnerability Database
  • Added to CISA KEV (detected)
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • Record created in this database
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • 2022
  • Added to CISA KEV catalog
    Jan 27, 2022 · CISA
  • 2021
  • CVE published
    Dec 8, 2021 · sonicwall

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 13, 2026 – Oct 13, 2026
  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

7 on the record

Elsewhere on this site

Sonicwall
every CVE for this vendor
2022-01
what else CISA listed that month
Memory corruption
same class
CWE-121
other pages naming this weakness

Related CVEs (same products)

  • CVE-2025-40603 Insertion of Sensitive Information into Log File in Sonicwall Sma 210 Firmware Oct 31, 2025
  • CVE-2024-38475 Apache HTTP Server Improper Escaping of Output Vulnerability KEV Jul 1, 2024
  • CVE-2023-44221 SonicWall SMA100 Appliances OS Command Injection Vulnerability KEV Dec 5, 2023
  • CVE-2021-20035 SonicWall SMA100 Appliances OS Command Injection Vulnerability KEV Sep 27, 2021
  • CVE-2021-20028 SonicWall Secure Remote Access (SRA) SQL Injection Vulnerability KEV Aug 4, 2021
  • CVE-2021-20016 SonicWall SSLVPN SMA100 SQL Injection Vulnerability KEV Feb 4, 2021

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2021-20038 is "SonicWall SMA 100 Appliances Stack-Based Buffer Overflow Vulnerability", rated Critical. It affects Sma 200 Firmware (Sonicwall); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 9.8 describes technical severity. EPSS 99.91% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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