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HomeCVEsCVE-2021-20021

CVE-2021-20021

Published: January 27, 2026
Last updated:9 hours ago (January 27, 2026)
Exploit: YesZero-day: YesPatch: YesTrend: Neutral
TL;DR
Updated January 27, 2026

CVE-2021-20021 is a critical severity vulnerability with a CVSS score of 9.8. Exploits are available; patches have been released and should be applied urgently. This is classified as a zero-day vulnerability.

Key Points
  • 1Critical severity (CVSS 9.8/10)
  • 2EPSS: 90.00% - very high likelihood of exploitation
  • 3Public exploits are available
  • 4Vendor patches are available
  • 5Strobes Priority Score: 885/1000 (High)
  • 6Affects products from: Sonicwall, Microsoft
Severity Scores
CVSS v39.8
CVSS v27.5
Priority Score885.0
EPSS Score90.0
Critical
Exploitation LikelihoodCritical
90.00%EPSS

Very high probability of exploitation in the next 30 days

Immediate patching required
90.00%
EPSS
9.8
CVSS
Yes
Exploit
Yes
Patch
Critical Priority
high EPSS • exploit exists • critical severity

EPSS predicts the probability of exploitation in the next 30 days based on real-world threat data, complementing CVSS severity scores with actual risk assessment.

Description

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.

CVSS v3 Breakdown
Attack Vector:Network
Attack Complexity:Local
Privileges Required:Network
User Interaction:Network
Scope:Unchanged
Confidentiality:High
Integrity:High
Availability:High
Exploit References
Cisa.govGitHubNucleiProofpoint Emerging Threats
Patch References
[email protected]Zeroday CZ
Trend Analysis
Neutral
Vulnerable Products
VendorProduct
SonicwallEmail Security Appliance 5000
SonicwallEmail Security Appliance 7050 Firmware
SonicwallEmail Security Appliance 8300 Firmware
SonicwallEmail Security Appliance 8300
SonicwallEmail Security Appliance 3300 Firmware
SonicwallEmail Security Appliance 4300 Firmware
SonicwallEmail Security Appliance 5000 Firmware
SonicwallEmail Security Appliance 5050 Firmware
SonicwallEmail Security Appliance 7000
SonicwallEmail Security Appliance 3300

And 10 more...

Advisories
CISA: 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.
GitHub AdvisoryNVD
Cite This Page
APA Format
Strobes VI. (2026). CVE-2021-20021 - CVE Details and Analysis. Strobes VI. Retrieved January 27, 2026, from https://vi.strobes.co/cve/CVE-2021-20021
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