NetExtender: Improper Link Resolution Before File Access
CVE-2026-66153 is a high-severity improper link resolution before file access vulnerability in NetExtender from SonicWall, with a CVSS 3.1 base score of 7.0 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. Affected NetExtender versions: 10.3.5 and earlier versions. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.24% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of NetExtender you run against the affected versions below, and install the vendor's latest release.
- 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 | NetExtender | 10.3.5 and earlier versions | Not stated |
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
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- LowA basic user account is enough.
- 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:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CISA (ADP).
Official description
The NEService auto-upgrade process insecurely handles temporary files in SonicWall NetExtender Linux client which allows an attacker to manipulate file paths.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Link Resolution Before File Access
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
How developers prevent this class of flaw
- Follow the principle of least privilege when assigning access rights to entities in a software system. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.
More Improper Link Resolution Before File Access vulnerabilities (CWE-59)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in NetExtender
- 7.2 High severity
- 7.2 High severity
- 7.2 High severity
- 8.8 High severity
- 7.3 High severity
- 7.8 High severity
Recent Improper Link Resolution Before File Access vulnerabilities
- 7.8 High severity
- 8.4 High severity
- 7.5 High severity
- 9.9 Critical severity
- 9.3 Critical severity
- 8.4 High severity
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