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Weekly Signal
Live intelligence Updated 20 Aug 2026 · 01:51 UTC

SonicWall · Email Security, Email Security Appliance 3300 Firmware, Email Security Appliance 4300 Firmware +9 more

CVE-2021-20021

SonicWall Email Security Improper Privilege Management Vulnerability

Recommended action

Treat this as an immediate remediation priority. Apply updates per vendor instructions.

View response plan
CVSS9.8
EPSS83.4%
KEVYes
ExploitationConfirmed exploitation
PatchPatch or guidance available ↓

Assessment

Why it matters

CISA lists this vulnerability as known to be exploited; exploitation is confirmed; EPSS is 83.4%; technical severity is CVSS 9.8.

A vulnerability in the SonicWall Email Security version 10.0.9.x allows an attacker to create an administrative account by sending a crafted HTTP request to the remote host.

Who should care

  • Teams operating Email Security, Email Security Appliance 3300 Firmware, Email Security Appliance 4300 Firmware +9 more
  • Vulnerability and exposure management teams
  • Security operations teams monitoring exploitation activity

Response plan

What I would do

  1. Confirm whether Email Security, Email Security Appliance 3300 Firmware, Email Security Appliance 4300 Firmware +9 more is present in the environment.
  2. Identify affected versions and establish whether vulnerable services are exposed or reachable.
  3. Apply updates per vendor instructions.
  4. Review relevant security telemetry for evidence of attempted or successful exploitation.
  5. Document the remediation decision and track it to verified completion.

Vendor remediation

Patch and remediation links

Use the vendor source below to confirm the correct fixed version, package or mitigation for your affected product.

Technical details

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE
CWE-306
Affected versions
SonicWall Email Security (End Excluding: 10.0.9.6103); SonicWall Email Security Appliance 3300 Firmware (End Excluding: 10.0.9.6105); SonicWall Email Security Appliance 4300 Firmware (End Excluding: 10.0.9.6105); SonicWall Email Security Appliance 5000 Firmware (End Excluding: 10.0.9.6105); SonicWall Email Security Appliance 5050 Firmware (End Excluding: 10.0.9.6105); SonicWall Email Security Appliance 7000 Firmware (End Excluding: 10.0.9.6105); SonicWall Email Security Appliance 7050 Firmware (End Excluding: 10.0.9.6105); SonicWall Email Security Appliance 8300 Firmware (End Excluding: 10.0.9.6105)
Published
9 April 2021
Attack vector
Network
Privileges required
None
User interaction
None

Signal timeline

  1. CVE published
  2. Added to CISA KEV
  3. Latest EPSS score: 83.4%
  4. Signal calculated at 86

External references

Live public intelligence This assessment combines public-source evidence. Validate the affected product, version and exposure against your own environment before making a risk decision.