How severe is CVE-2021-20021?

CVE-2021-20021 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-20021 being actively exploited?

Yes. CVE-2021-20021 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2021-11-03, which means active exploitation has been confirmed. It should be prioritised for remediation.

What products are affected by CVE-2021-20021?

CVE-2021-20021 primarily affects Sonicwall Email Security. In total, 11 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-20021?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.

Does CVE-2021-20021 have an EU (EUVD) identifier?

Yes. CVE-2021-20021 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-7484. It is also flagged as exploited in the EUVD (since 2021-11-03).

When was CVE-2021-20021 published?

CVE-2021-20021 was published on 2021-04-09 and last updated on 2026-08-12.

CVE-2021-20021

CVE-2021-20021 is a critical-severity vulnerability in Sonicwall Email Security with a CVSS 3.x base score of 9.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2021-11-03). The underlying weakness is classified as CWE-269.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 83% (100th percentile)
Actively exploited: Yes — listed in CISA KEV (added 2021-11-03)
EU (EUVD) id: EUVD-2021-7484
EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2021-11-03)
Weakness: CWE-269
Affected product: Sonicwall Email Security
Published: 2021-04-09
Last modified: 2026-08-12

Description

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.

Frequently asked questions

What is CVE-2021-20021?: 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 severe is CVE-2021-20021?: CVE-2021-20021 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-20021 being actively exploited?: Yes. CVE-2021-20021 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2021-11-03, which means active exploitation has been confirmed. It should be prioritised for remediation.
What products are affected by CVE-2021-20021?: CVE-2021-20021 primarily affects Sonicwall Email Security. In total, 11 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-20021?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.
Does CVE-2021-20021 have an EU (EUVD) identifier?: Yes. CVE-2021-20021 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-7484. It is also flagged as exploited in the EUVD (since 2021-11-03).
When was CVE-2021-20021 published?: CVE-2021-20021 was published on 2021-04-09 and last updated on 2026-08-12.

References

Affected products (11)

cpe:2.3:a:sonicwall:email_security:*:*:*:*:*:*:*:*
cpe:2.3:o:sonicwall:email_security_appliance_9000_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:sonicwall:email_security_appliance_3300_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:sonicwall:email_security_appliance_4300_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:sonicwall:email_security_appliance_8300_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:sonicwall:email_security_appliance_5000_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:sonicwall:email_security_appliance_7000_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:sonicwall:email_security_appliance_5050_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:sonicwall:email_security_appliance_7050_firmware:*:*:*:*:*:*:*:*
cpe:2.3:a:sonicwall:email_security_virtual_appliance:*:*:*:*:*:*:*:*
cpe:2.3:a:sonicwall:hosted_email_security:*:*:*:*:*:*:*:*

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