SonicWall Email Security Path Traversal
CVE-2021-20023 is a medium-severity improper limitation of a pathname to a restricted directory vulnerability in Email Security from SonicWall, with a CVSS 3.1 base score of 4.9 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.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Email Security Appliance 9000 Firmware to 10.0.9.6177 or a later version.
- Update Email Security Appliance 3300 Firmware to 10.0.9.6177 or a later version.
- Update Email Security Appliance 4300 Firmware to 10.0.9.6177 or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on psirt.global.sonicwall.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| SonicWall | Email Security | 10.0.9 and earlier | Not stated |
| SonicWall | Email Security Appliance 9000 Firmware | before 10.0.9.6177 | 10.0.9.6177 |
| SonicWall | Email Security Appliance 3300 Firmware | before 10.0.9.6177 | 10.0.9.6177 |
| SonicWall | Email Security Appliance 4300 Firmware | before 10.0.9.6177 | 10.0.9.6177 |
| SonicWall | Email Security Appliance 8300 Firmware | before 10.0.9.6177 | 10.0.9.6177 |
| SonicWall | Email Security Appliance 5000 Firmware | before 10.0.9.6177 | 10.0.9.6177 |
| SonicWall | Email Security Appliance 7000 Firmware | before 10.0.9.6177 | 10.0.9.6177 |
| SonicWall | Email Security Appliance 5050 Firmware | before 10.0.9.6177 | 10.0.9.6177 |
| SonicWall | Email Security Appliance 7050 Firmware | before 10.0.9.6177 | 10.0.9.6177 |
| SonicWall | Email Security Virtual Appliance | before 10.0.9.6177 | 10.0.9.6177 |
| SonicWall | Hosted Email Security | before 10.0.9.6173 | 10.0.9.6173 |
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
- NoneNothing can be modified.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 4.9 | Medium | NVD |
| CVSS 3.1 | 4.9 | Medium | CISA (ADP) |
| CVSS 2.0 | 4.0 | Medium | NVD |
Official description
SonicWall Email Security version 10.0.9.x contains a vulnerability that allows a post-authenticated attacker to read an arbitrary file on the remote host.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Limitation of a Pathname to a Restricted Directory
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
How developers prevent this class of flaw
- For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
- Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.
More Improper Limitation of a Pathname to a Restricted Directory vulnerabilities (CWE-22)
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-20023US Government Resource
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