Dnn.Platform: Improper Neutralization of Alternate XSS Syntax
CVE-2026-40321 is a high-severity improper neutralization of alternate XSS syntax vulnerability in Dnn.Platform from Dnnsoftware, with a CVSS 3.1 base score of 8.0 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, but only if a user takes part, for example by opening a link or file. Affected Dnn.Platform versions: < 10.2.2. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 6.52% chance of exploitation within 30 days, which is in the top 6.11% of all scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Dotnetnuke to 10.2.2 or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Dnnsoftware | Dnn.Platform | < 10.2.2 | Not stated |
| Dnnsoftware | Dotnetnuke | before 10.2.2 | 10.2.2 |
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
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- LowA basic user account is enough.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- 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:H/PR:L/UI:R/S:C/C:H/I:H/A:H. Scored by CNA (github.com).
Official description
DNN (formerly DotNetNuke) is an open-source web content management platform (CMS) in the Microsoft ecosystem. Prior to version 10.2.2, a user could upload a specially crafted SVG file that could include scripts that can target both authenticated and unauthenticated DNN users. The impact is increased if the scripts are run by a power user. Version 10.2.2 patches the issue.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Alternate XSS Syntax
The product does not neutralize or incorrectly neutralizes user-controlled input for alternate script syntax.
How developers prevent this class of flaw
- Resolve all input to absolute or canonical representations before processing.
- With Struts, write all data from form beans with the bean's filter attribute set to true.
More Improper Neutralization of Alternate XSS Syntax vulnerabilities (CWE-87)
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
Patches and release notes
Other vulnerabilities in Dnn.Platform
- 9.8 Critical severity
- 9.0 Critical severity
- 8.6 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
Recent Improper Neutralization of Alternate XSS Syntax vulnerabilities
- 8.8 High severity
- 8.8 High severity
- 9.3 Critical severity
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