What is CVE-2026-66798?

CVE-2026-66798 is a medium-severity vulnerability in Microsoft Edge Chromium, classified under Use After Free. CVSS score: 4.3/10. Published 2026-08-28.

How severe is CVE-2026-66798?

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

Use After Free in Microsoft Edge Chromium

CVE-2026-66798

Use after free in Microsoft Edge (Chromium-based) allows an unauthorized attacker to execute code over a network.

Vulnerability class: Use-After-Free

Published 2026-08-28 · last modified 2026-09-11.

CVSS v3 metric

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

EPSS exploit prediction

EPSS: 0.008 (54.9th percentile), scored 2026-10-13.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 55th percentile — 54.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.006 · newest: 0.008 · change: +0.002

Affected products

Weakness classification (CWE)

CWE-416 — Use After Free

References

Microsoft Edge (Chromium-based) Remote Code Execution Vulnerability (vendor-advisory, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2026-66798?: CVE-2026-66798 is a medium-severity vulnerability in Microsoft Edge Chromium, classified under Use After Free. CVSS score: 4.3/10. Published 2026-08-28.
How severe is CVE-2026-66798?: Medium severity. CVSS v3 base score is 4.3 out of 10.