What is CVE-2026-40321?

CVE-2026-40321 is a high-severity vulnerability in Dnnsoftware Dnn.platform, classified under Improper Neutralization of Alternate XSS Syntax. CVSS score: 8.0/10. Published 2026-04-17.

How severe is CVE-2026-40321?

High severity. CVSS v3 base score is 8.0 out of 10.

XSS in Dnnsoftware Dnn.platform

CVE-2026-40321

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.

Published 2026-04-17 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.0 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.004 (28.6th percentile), scored 2026-10-19.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 29th percentile — 28.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.064 · newest: 0.004 · change: -0.060

Affected products

Dnnsoftware Dnn.platform — versions < 10.2.2
Dnnsoftware Dotnetnuke

Weakness classification (CWE)

CWE-87 — Improper Neutralization of Alternate XSS Syntax

References

github.com/dnnsoftware/Dnn.Platform/security/advisories/GHSA-ffq7-898w-9jc4 (Vendor Advisory)
github.com/dnnsoftware/Dnn.Platform/releases/tag/v10.2.2 (Release Notes)

Frequently asked questions

What is CVE-2026-40321?: CVE-2026-40321 is a high-severity vulnerability in Dnnsoftware Dnn.platform, classified under Improper Neutralization of Alternate XSS Syntax. CVSS score: 8.0/10. Published 2026-04-17.
How severe is CVE-2026-40321?: High severity. CVSS v3 base score is 8.0 out of 10.