What is CVE-2021-30621?

CVE-2021-30621 is a medium-severity vulnerability in Microsoft Edge, classified under Authentication Bypass by Spoofing. CVSS score: 6.5/10. Published 2021-09-03.

How severe is CVE-2021-30621?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Microsoft Edge

CVE-2021-30621

Chromium: CVE-2021-30621 UI Spoofing in Autofill

Published 2021-09-03 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N.

EPSS exploit prediction

EPSS: 0.035 (88.7th percentile), scored 2026-10-01.

Low probability of exploitation in the next 30 days, but still tracked. 89th percentile — 88.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.035 · newest: 0.035 · change: 0.000

Affected products

Microsoft Edge
Microsoft Edge Chromium
Microsoft Edge (Chromium-Based) — versions unspecified
Fedoraproject Fedora — versions 35

Weakness classification (CWE)

CWE-290 — Authentication Bypass by Spoofing

References

portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-30621 (Patch, Vendor Advisory)
lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)

Frequently asked questions

What is CVE-2021-30621?: CVE-2021-30621 is a medium-severity vulnerability in Microsoft Edge, classified under Authentication Bypass by Spoofing. CVSS score: 6.5/10. Published 2021-09-03.
How severe is CVE-2021-30621?: Medium severity. CVSS v3 base score is 6.5 out of 10.