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CVE-2021-20021

96
FAUCET Score

CVE-2021-20021 is a critical vulnerability in SonicWall Email Security versions 10.0.9.x that allows an unauthenticated attacker to create an administrative account by sending a specially crafted HTTP request. With a CVSS score of 9.8, this flaw is easily exploitable over the network with no user interaction, leading to complete compromise of confidentiality, integrity, and availability. The vulnerability is actively exploited in the wild, including in known ransomware campaigns like HelloKitty, and has garnered significant community and media attention, despite the lack of public Metasploit or ExploitDB modules.

Impacted Technologies

VendorProductVersion(s)CPE
< 10.0.9.6103CPE matchmatch criteria
cpe:2.3:a:sonicwall:email_security:*:*:*:*:*:*:*:*
< 10.0.9.6105CPE matchmatch criteria
cpe:2.3:o:sonicwall:email_security_appliance_9000_firmware:*:*:*:*:*:*:*:*
< 10.0.9.6105CPE matchmatch criteria
cpe:2.3:o:sonicwall:email_security_appliance_3300_firmware:*:*:*:*:*:*:*:*
< 10.0.9.6105CPE matchmatch criteria
cpe:2.3:o:sonicwall:email_security_appliance_4300_firmware:*:*:*:*:*:*:*:*
< 10.0.9.6105CPE matchmatch criteria
cpe:2.3:o:sonicwall:email_security_appliance_8300_firmware:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
83.43%
Probability of exploitation in next 30 days
EPSS Percentile
99.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
Added to KEV · Nov 3, 2021
Nuclei: CVE-2021-20021 · Sep 26, 2025
This CVE's current EPSS score of 0.8343 is in the 98th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

cisa.gov / known-exploited-vulnerabilities-catalog
US Government Resource
psirt.global.sonicwall.com / vuln-detail/SNWLID-2021-0007
Vendor Advisory