Threats / SonicWall / CVE-2021-20021
CVE-2021-20021
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
SonicWall Email Security vulnerability
SonicWall Email Security contains an improper privilege management flaw allowing unauthenticated attackers to create administrative accounts via crafted HTTP requests, enabling full system compromise.
Verdict
Today item, not a backlog item.
This vulnerability permits remote privilege escalation without authentication. Attackers can establish persistent administrative access to email security infrastructure, facilitating data exfiltration, email interception, and lateral network movement.
CISA KEV Yes · 2021-11-035Ransomware use Flagged5EPSS 0.83425 (verify live)6CVSS 9.8 (CISA)4CISA SSVC Exploitation: active · Automatable: yes · Impact: total4Exploit Public PoC / detection · nuclei template12
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
9 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 2021-11-03), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.83425 — 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, SonicWall Email Security. 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-269 Improper Privilege Management — weakness family: Authorization / access control.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 208 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 specially crafted HTTP request to the SonicWall Email Security appliance to create an administrative account without authentication.
Business
Attackers gain unauthorized administrative access to email security controls, bypassing all authentication mechanisms.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I use the newly created admin account to modify email filtering rules, access stored messages, and establish persistence.
Business
Email communications become fully compromised; sensitive business correspondence is exposed or intercepted at the security gateway.
3
Lateral reach — past segmentation narrative 3
Attacker
I chain this exploit with CVE-2021-20022 and CVE-2021-20023 to escalate privileges further and move laterally into the internal network.
Business
The compromised email appliance becomes a pivot point for network-wide intrusion, enabling ransomware deployment and data theft operations.
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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