How severe is CVE-2021-21805?

CVE-2021-21805 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-2021-21805 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 70% (99th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21805?

CVE-2021-21805 affects Advantech R-seenet. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-21805?

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-2021-21805 published?

CVE-2021-21805 was published on 2021-08-05 and last updated on 2026-06-17.

CVE-2021-21805

CVE-2021-21805 is a critical-severity vulnerability in Advantech R-seenet with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 70% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-78.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 10.0
EPSS exploit prediction: 70% (99th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-78
Affected product: Advantech R-seenet
Published: 2021-08-05
Last modified: 2026-06-17

Description

An OS Command Injection vulnerability exists in the ping.php script functionality of Advantech R-SeeNet v 2.4.12 (20.10.2020). A specially crafted HTTP request can lead to arbitrary OS command execution. An attacker can send a crafted HTTP request to trigger this vulnerability.

Frequently asked questions

What is CVE-2021-21805?: An OS Command Injection vulnerability exists in the ping.php script functionality of Advantech R-SeeNet v 2.4.12 (20.10.2020). A specially crafted HTTP request can lead to arbitrary OS command execution. An attacker can send a crafted HTTP request to trigger this vulnerability.
How severe is CVE-2021-21805?: CVE-2021-21805 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-2021-21805 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 70% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21805?: CVE-2021-21805 affects Advantech R-seenet. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-21805?: 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-2021-21805 published?: CVE-2021-21805 was published on 2021-08-05 and last updated on 2026-06-17.

References

https://talosintelligence.com/vulnerability_reports/TALOS-2021-1274

Affected products (1)

cpe:2.3:a:advantech:r-seenet:2.4.12:*:*:*:*:*:*:*

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