What is CVE-2021-33266?

CVE-2021-33266 is a critical-severity vulnerability in Dlink Dir-809, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2021-12-01.

How severe is CVE-2021-33266?

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

Buffer overflow in Dlink Dir-809

CVE-2021-33266

D-Link DIR-809 devices with firmware through DIR-809Ax_FW1.12WWB03_20190410 were discovered to contain a stack buffer overflow vulnerability in the function FUN_8004776c in /formVirtualApp. This vulnerability is triggered via a crafted POST request.

Vulnerability class: Buffer Overflow

Published 2021-12-01 · 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: 0.169 (97.0th percentile), scored 2026-10-02.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 97th percentile — 97.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.169 · newest: 0.169 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

www.dlink.com/en/security-bulletin/ (Vendor Advisory)
github.com/Lnkvct/IoT-poc/tree/master/D-Link-DIR809/vuln04 (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2021-33266?: CVE-2021-33266 is a critical-severity vulnerability in Dlink Dir-809, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2021-12-01.
How severe is CVE-2021-33266?: Critical severity. CVSS v3 base score is 9.8 out of 10.