CyberSecBulletin
CVE-2021-20022Exploited in the wildNVD status: Analyzed

SonicWall Email Security Unrestricted Upload of File

Published Updated By the CyberSecBulletin desk

CVE-2021-20022 is a high-severity unrestricted upload of file with dangerous type vulnerability in Email Security from SonicWall, with a CVSS 3.1 base score of 7.2 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, without any action from a user. Affected Email Security versions: 10.0.9 and earlier. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on November 3, 2021, which means attacks have been observed in the wild, including in ransomware campaigns.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Email Security Appliance 9000 Firmware to 10.0.9.6105 or a later version.
  2. Update Email Security Appliance 3300 Firmware to 10.0.9.6105 or a later version.
  3. Update Email Security Appliance 4300 Firmware to 10.0.9.6105 or a later version.
  4. CISA's required action: Apply updates per vendor instructions.
  5. Read the advisory on psirt.global.sonicwall.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
SonicWallEmail Security10.0.9 and earlierNot stated
SonicWallEmail Security Appliance 9000 Firmwarebefore 10.0.9.610510.0.9.6105
SonicWallEmail Security Appliance 3300 Firmwarebefore 10.0.9.610510.0.9.6105
SonicWallEmail Security Appliance 4300 Firmwarebefore 10.0.9.610510.0.9.6105
SonicWallEmail Security Appliance 8300 Firmwarebefore 10.0.9.610510.0.9.6105
SonicWallEmail Security Appliance 5000 Firmwarebefore 10.0.9.610510.0.9.6105
SonicWallEmail Security Appliance 7000 Firmwarebefore 10.0.9.610510.0.9.6105
SonicWallEmail Security Appliance 5050 Firmwarebefore 10.0.9.610510.0.9.6105
SonicWallEmail Security Appliance 7050 Firmwarebefore 10.0.9.610510.0.9.6105
SonicWallEmail Security Virtual Appliancebefore 10.0.9.610510.0.9.6105
SonicWallHosted Email Securitybefore 10.0.9.610310.0.9.6103

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
HighAdministrator-level access is required first.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.17.2HighNVD
CVSS 3.17.2HighCISA (ADP)
CVSS 2.07.5HighNVD

Official description

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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Unrestricted Upload of File with Dangerous Type

The product allows the upload or transfer of dangerous file types that are automatically processed within its environment.

How developers prevent this class of flaw

  • Generate a new, unique filename for an uploaded file instead of using the user-supplied filename, so that no external input is used at all.
  • When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
  • Consider storing the uploaded files outside of the web document root entirely. Then, use other mechanisms to deliver the files dynamically.

More Unrestricted Upload of File with Dangerous Type vulnerabilities (CWE-434)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. Deadline for US federal agencies to remediate, set by CISA.
  4. CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
  5. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Other vulnerabilities in Email Security

All Email Security vulnerabilities

Recent Unrestricted Upload of File with Dangerous Type vulnerabilities

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