What is CVE-2021-38408?

CVE-2021-38408 is a critical-severity vulnerability in Advantech Webaccess, classified under Stack-based Buffer Overflow. CVSS score: 9.8/10. Published 2021-09-09.

How severe is CVE-2021-38408?

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

Buffer overflow in Advantech Webaccess

CVE-2021-38408

A stack-based buffer overflow vulnerability in Advantech WebAccess Versions 9.02 and prior caused by a lack of proper validation of the length of user-supplied data may allow remote code execution.

Vulnerability class: Buffer Overflow

Published 2021-09-09 · 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: 0.116 (96.0th percentile), scored 2026-10-23.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 96th percentile — 96.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.116 · newest: 0.116 · change: 0.000

Affected products

Advantech Webaccess
Advantech Webaccess — versions WebAccess: Versions 9.02 and prior

Weakness classification (CWE)

CWE-121 — Stack-based Buffer Overflow

References

us-cert.cisa.gov/ics/advisories/icsa-21-245-03 (US Government Resource, Third Party Advisory)

Frequently asked questions

What is CVE-2021-38408?: CVE-2021-38408 is a critical-severity vulnerability in Advantech Webaccess, classified under Stack-based Buffer Overflow. CVSS score: 9.8/10. Published 2021-09-09.
How severe is CVE-2021-38408?: Critical severity. CVSS v3 base score is 9.8 out of 10.