Threats / SonicWall / CVE-2021-20023
CVE-2021-20023
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
SonicWall Email Security vulnerability
SonicWall Email Security contains a path traversal vulnerability allowing authenticated attackers to read arbitrary files, exploited in ransomware campaigns via a multi-CVE chain for privilege escalation.
Verdict
Today item, not a backlog item.
Post-authenticated path traversal in SonicWall Email Security enables file disclosure and serves as part of a known exploit chain for privilege escalation. Active exploitation in ransomware operations confirms real-world threat.
CISA KEV Yes · 2021-11-035Ransomware use Flagged5EPSS 0.50234 (verify live)6CVSS 4.9 (CISA)4CISA SSVC Exploitation: active · Automatable: no · Impact: partial4
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 0.50234 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 4.9 (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N) · 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-22 Path Traversal — weakness family: Path traversal / file.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: partialCISA'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 197 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.
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 gain initial access to SonicWall Email Security as an authenticated user.
Business
Attacker establishes foothold within email security infrastructure.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I exploit the path traversal flaw to read sensitive configuration and system files on the host.
Business
Confidential data and system details are exposed to the attacker.
3
Lateral reach — past segmentation narrative 3
Attacker
I combine this disclosure with CVE-2021-20021 and CVE-2021-20022 to escalate privileges on the system.
Business
Attacker gains administrative control of the email security appliance.
4
Data at risk — exfiltration narrative 4
Attacker
I use elevated privileges to deploy ransomware or establish persistent access.
Business
Organization faces encryption of critical systems and operational disruption.
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