What is CVE-2021-39306?

CVE-2021-39306 is a critical-severity vulnerability in Realtek Rtl8195am, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2021-12-22.

How severe is CVE-2021-39306?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Buffer overflow in Realtek Rtl8195am

CVE-2021-39306

A stack buffer overflow was discovered on Realtek RTL8195AM device before 2.0.10, it exists in the client code when an attacker sends a big size Authentication challenge text in WEP security.

Vulnerability class: Buffer Overflow

Published 2021-12-22 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.013 (68.6th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 69th percentile — 68.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.013 · newest: 0.013 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

www.realtek.com (Vendor Advisory)
www.amebaiot.com/en/security_bulletin/cve-2021-39306/ (Vendor Advisory)

Frequently asked questions

What is CVE-2021-39306?: CVE-2021-39306 is a critical-severity vulnerability in Realtek Rtl8195am, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2021-12-22.
How severe is CVE-2021-39306?: Critical severity. CVSS v3 base score is 9.8 out of 10.