CVE-2021-20022 KEVRansomware High · 7.2 EPSS 16.6%
SonicWall Email Security Unrestricted Upload of File Vulnerability
SonicWall · SonicWall Email Security
Summary
The flaw is an unrestricted file upload vulnerability in the SonicWall Email Security product, affecting version 10.0.9.x. An attacker who can reach the appliance over the network and holds valid credentials (post-authentication) can upload an arbitrary file to the remote host, with no user interaction required.
Official description · NVD
SonicWall Email Security version 10.0.9.x contains a vulnerability that allows a post-authenticated attacker to upload an arbitrary file to the remote host.
Priority scorePatchfirst’s 0 to 100 ranking. It adds points for CISA KEV listing, ransomware use, EPSS, threat reports, public exploit code and CVSS. Every CVE page shows the breakdown. Breakdown
72.4 / 100
- Exploited
- Yes, in CISA KEV
- Reports
- 0
- Tactics
- 5/15
How an attack unfolds
Based on MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. mappings. Select a step to see the evidence.How attackers get in
What they do
Exploitation timelineDated milestones for a CVE: when it was disclosed, when exploit code became public, when exploitation was confirmed, and when threat reports named it.
First seen exploited 11 days after disclosure.
- Disclosedday 0
- First seen exploitedVulnCheck KEV evidence+11 days
- Added to CISA KEVknown ransomware use; EU database agrees+7 mo
CISA KEV listing is when exploitation was confirmed, not necessarily the first attack.
MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. techniques
2 TechniqueOne specific attacker behaviour in MITRE ATT&CK, such as T1190 “Exploit Public-Facing Application”. IDs with a dot, like T1059.004, are sub-techniques., grouped by TacticThe attacker’s goal at a stage of an attack in MITRE ATT&CK, such as Initial Access or Persistence. Each technique belongs to one or more tactics. in kill-chain order, 2 cited passages 2Initial AccessTA0001
Valid Accounts T1078 Medium Confidence (technique links)How sure Patchfirst is that an ATT&CK technique applies to this CVE. High and medium links are shown by default; low ones come from early or generic mappings, text matching, or contradict the CVE’s details. also Persistence, Privilege Escalation, Stealth
AI mapping from the description · how it is exploited
Requires authenticated account access to exploit
allows a post-authenticated attacker to upload
Command and ControlTA0011
Ingress Tool Transfer T1105 Medium Confidence (technique links)How sure Patchfirst is that an ATT&CK technique applies to this CVE. High and medium links are shown by default; low ones come from early or generic mappings, text matching, or contradict the CVE’s details.
AI mapping from the description · primary impact
Arbitrary file upload delivers attacker tooling to host
allows a post-authenticated attacker to upload an arbitrary file to the remote host
Detection
0 rules for this CVE · 143 general rules for its techniquesRules for this CVE
0Sigma ruleAn open, vendor-neutral detection rule for log data. Security teams convert Sigma rules into searches for their own SIEM. that reference CVE-2021-20022 directly.CVE-specific rules are not available in this build. Search SigmaHQ ↗
General rules for this CVE’s techniques
These detect the technique in general, not this specific vulnerability.
Valid AccountsT107856 general rules
- Win Susp Computer Name Containing Samtheadmincriticaltest
- Account Created And Deleted Within A Close Time Framehightest
- Activity From Anonymous IP Addresshightest
- Atypical Travelhightest
- Azure AD Threat Intelligencehightest
- Azure Subscription Permission Elevation Via AuditLogshightest
- External Remote SMB Logon from Public IPhightest
- Impossible Travelhightest
Ingress Tool TransferT110587 general rules
- Greenbug Espionage Group Indicatorscriticaltest
- Pandemic Registry Keycriticaltest
- Curl Download And Execute Combinationhightest
- File Download And Execution Via IEExec.EXEhightest
- File Download From IP Based URL Via CertOC.EXEhightest
- File Download Using Notepad++ GUP Utilityhightest
- File Download Via Bitsadmin To A Suspicious Target Folderhightest
- File Download Via Windows Defender MpCmpRun.EXEhightest
Sigma rules © SigmaHQ, Detection Rule License 1.1; linked, not reproduced.
What security researchers reported
Not named in any threat report yetAlso mentioned in 50 community threat pulses (AlienVault OTX)
Weaker evidencePulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.
- Actively_Exploited_Kev | Oct 29, 202628 Oct 2026
- Actively_Exploited_Kev | Oct 28, 202627 Oct 2026
- Actively_Exploited_Kev | Oct 27, 202626 Oct 2026
- Actively_Exploited_Kev | Oct 24, 202623 Oct 2026
- Actively_Exploited_Kev | Oct 23, 202622 Oct 2026
- Actively_Exploited_Kev | Oct 22, 202621 Oct 2026
- 44 more on OTX