How to check if you are exposed to CVE-2021-20021
- Find every SonicWall Email Security system you or your clients run, including ones exposed to the internet. Those come first: CISA only lists flaws attackers are already using.
- Compare each version with the fixed versions in the vendor advisory. Where no fix exists yet, apply the vendor’s mitigation or take the system off the internet.
- Run a credentialed vulnerability scan to catch the systems you missed, then check that the next scan no longer reports CVE-2021-20021.
US federal agencies had to fix this by 2021-11-17. Everyone else should treat that deadline as a guide: if it has passed, this is overdue.
Affected versions
Versions the National Vulnerability Database lists as vulnerable to CVE-2021-20021. Check the vendor advisory for the exact fixed builds before you sign anything off.
| Product | Vulnerable versions |
|---|---|
| SonicWall Email Security | before 10.0.9.6103 |
| SonicWall Email Security Appliance 9000 Firmware | before 10.0.9.6105 |
| SonicWall Email Security Appliance 3300 Firmware | before 10.0.9.6105 |
| SonicWall Email Security Appliance 4300 Firmware | before 10.0.9.6105 |
| SonicWall Email Security Appliance 8300 Firmware | before 10.0.9.6105 |
| SonicWall Email Security Appliance 5000 Firmware | before 10.0.9.6105 |
NVD lists 5 more affected products; see the full record on NVD.
Timeline
- · Published in the National Vulnerability Database
- · Added to CISA's Known Exploited Vulnerabilities catalog, 208 days after it was published
- · Fix-by date for US federal agencies, passed 1,810 days ago
Weakness type
More exploited SonicWall vulnerabilities
CISA lists 19 exploited SonicWall vulnerabilities. The closest matches:
- CVE-2021-20023SonicWall Email Security Path Traversal VulnerabilityAdded 2021-11-03
- CVE-2021-20022SonicWall Email Security Unrestricted Upload of File VulnerabilityAdded 2021-11-03
- CVE-2026-83549SonicWall SMA1000 Appliances OS Command Injection VulnerabilityAdded 2026-09-02
- CVE-2026-83548SonicWall SMA1000 Appliances Server-Side Request Forgery VulnerabilityAdded 2026-09-02
- CVE-2026-15410SonicWall SMA1000 Appliances Code Injection VulnerabilityAdded 2026-07-14
- CVE-2026-15409SonicWall SMA1000 Appliances Server-Side Request Forgery VulnerabilityAdded 2026-07-14
- CVE-2025-40602SonicWall SMA1000 Missing Authorization VulnerabilityAdded 2025-12-17
- CVE-2023-44221SonicWall SMA100 Appliances OS Command Injection VulnerabilityAdded 2025-05-01
Keep going
Sources: CISA Known Exploited Vulnerabilities catalog (version 2026.10.30); EPSS data from FIRST.org; CVSS and descriptions from the NIST National Vulnerability Database. Checked 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.