Threats / SonicWall / CVE-2021-20038
CVE-2021-20038
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
SonicWall SMA 100 Appliances vulnerability
SonicWall SMA 100 Appliances contain an unauthenticated stack-based buffer overflow vulnerability enabling remote code execution without authentication.
Verdict
Today item, not a backlog item.
This vulnerability poses critical risk due to unauthenticated remote exploitation capability, high EPSS score, and confirmed active exploitation in ransomware campaigns. Immediate patching is required for all affected appliances.
CISA KEV Yes · 2022-01-285Ransomware use Flagged5EPSS 0.99912 (verify live)6Exploit Weaponized · public PoC7CVSS 9.8 (CISA)4CISA SSVC Exploitation: active · Automatable: yes · Impact: total4
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Fully weaponized — public exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
13 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-01-28), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.99912 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 9.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) · Affected: SonicWall, SMA 100 Appliances. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-121 Stack-based Buffer Overflow — weakness family: Memory safety.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: yes · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 51 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
Public exploit available
Public exploit tooling is catalogued for this CVE (a public proof-of-concept / detection template). Catalog entries: nuclei template. We link the catalog page(s) only — no payload or code is hosted or restated here.Link, never host — the catalog page is the source; basicsecurity.net does not redistribute payloads.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I send a crafted network request to the SMA 100 appliance without credentials, triggering a stack buffer overflow.
Business
The organization's perimeter security appliance becomes a direct attack vector accessible to any internet-connected threat actor.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I overflow the stack buffer to inject and execute arbitrary code on the appliance with system privileges.
Business
Attackers gain complete control of the security gateway, enabling lateral movement into the internal network and data exfiltration.
3
Lateral reach — past segmentation narrative 3
Attacker
I establish persistent access and deploy ransomware payloads across the compromised network infrastructure.
Business
Critical business systems are encrypted and held for ransom, resulting in operational shutdown and potential financial extortion.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05
Coverage & confidence
— what we know, and what we don’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by sonicwallCNA
Credited with finding itNo finder is named in the public CVE record or the scanned vendor advisory — attribution scoped to the sources checked.
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
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