How severe is CVE-2021-38408?

CVE-2021-38408 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-38408 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 12% (96th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-38408?

CVE-2021-38408 affects Advantech Webaccess. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-38408?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-38408 published?

CVE-2021-38408 was published on 2021-09-09 and last updated on 2026-06-17.

CVE-2021-38408

CVE-2021-38408 is a critical-severity vulnerability in Advantech Webaccess with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 12% places it in the 96th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-121.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 12% (96th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-121
Affected product: Advantech Webaccess
Published: 2021-09-09
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2021-38408?: CVE-2021-38408 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-38408 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 12% (96th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-38408?: CVE-2021-38408 affects Advantech Webaccess. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-38408?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-38408 published?: CVE-2021-38408 was published on 2021-09-09 and last updated on 2026-06-17.

References

https://us-cert.cisa.gov/ics/advisories/icsa-21-245-03

Affected products (1)

cpe:2.3:a:advantech:webaccess:*:*:*:*:*:*:*:*

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