CVE-2021-20021
CRITICALCISA KEVEPSS 100th pctlDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploit Intelligence
Very high risk: more likely to be exploited than 100% of all known CVEs.
SonicWall Email Security Improper Privilege Management Vulnerability
SonicWall Email Security contains an improper privilege management vulnerability that allows an attacker to create an administrative account by sending a crafted HTTP request to the remote host. This vulnerability has known usage in a SonicWall Email Security exploit chain along with CVE-2021-20022 and CVE-2021-20023 to achieve privilege escalation.
Apply updates per vendor instructions.
Remediation due: 2021-11-17
Associated with ransomware campaigns
References
Related Vulnerabilities
Other CWE-269 (Improper Privilege Management) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2017-12635 | Critical | 9.8 | 100% | - | Fix |
| CVE-2022-24637 | Critical | 9.8 | 99% | - | Fix |
| CVE-2017-5689 | Critical | 9.8 | 92% | KEV | Fix |
| CVE-2020-3243 | Critical | 9.8 | 88% | - | - |
| CVE-2024-21888 | High | 8.8 | 87% | - | - |
| CVE-2022-0441 | Critical | 9.8 | 85% | - | Fix |
Common questions
How do I fix CVE-2021-20021?
Published advisories record a fix for 11 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2021-20021 being actively exploited?
Yes. CVE-2021-20021 is listed in the CISA Known Exploited Vulnerabilities catalog, which means exploitation has been observed in the wild. CISA has also linked it to known ransomware campaigns. US federal agencies were required to remediate it by 2021-11-17. Treat it as a priority whatever its CVSS score says.
How severe is CVE-2021-20021?
CVE-2021-20021 has a CVSS v3 base score of 9.8, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2021-20021 affect?
Published advisories record a fix for email security (NVD), email security appliance 3300 firmware (NVD), email security appliance 4300 firmware (NVD), email security appliance 5000 firmware (NVD), and 7 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-11-10.