What is CVE-2021-3339?

CVE-2021-3339 is a medium-severity vulnerability in Microsoft Modernflow, classified under Improper Authentication. CVSS score: 4.3/10. Published 2021-02-19.

How severe is CVE-2021-3339?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Auth bypass in Microsoft Modernflow

CVE-2021-3339

ModernFlow before 1.3.00.208 does not constrain web-page access to members of a security group, as demonstrated by the Search Screen and the Profile Screen.

Vulnerability class: Broken Authentication

Published 2021-02-19 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.020 (80.3th percentile), scored 2026-10-07.

Low probability of exploitation in the next 30 days, but still tracked. 80th percentile — 80.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.019 · newest: 0.020 · change: +0.001

Affected products

Microsoft Modernflow

Weakness classification (CWE)

CWE-287 — Improper Authentication

References

appsource.microsoft.com/en-us/product/web-apps/acctech-systems-pty-ltd.modernfl… (Product)
4sightwebsite.azurewebsites.net/mf_releaseNotes (Broken Link)

Frequently asked questions

What is CVE-2021-3339?: CVE-2021-3339 is a medium-severity vulnerability in Microsoft Modernflow, classified under Improper Authentication. CVSS score: 4.3/10. Published 2021-02-19.
How severe is CVE-2021-3339?: Medium severity. CVSS v3 base score is 4.3 out of 10.