How severe is CVE-2021-21804?

CVE-2021-21804 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-2021-21804 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (88th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21804?

CVE-2021-21804 affects Advantech R-seenet. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-21804?

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-2021-21804 published?

CVE-2021-21804 was published on 2021-07-16 and last updated on 2026-06-17.

CVE-2021-21804

CVE-2021-21804 is a critical-severity vulnerability in Advantech R-seenet with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-829.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 4% (88th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-829
Affected product: Advantech R-seenet
Published: 2021-07-16
Last modified: 2026-06-17

Description

A local file inclusion (LFI) vulnerability exists in the options.php script functionality of Advantech R-SeeNet v 2.4.12 (20.10.2020). A specially crafted HTTP request can lead to arbitrary PHP code execution. An attacker can send a crafted HTTP request to trigger this vulnerability.

Frequently asked questions

What is CVE-2021-21804?: A local file inclusion (LFI) vulnerability exists in the options.php script functionality of Advantech R-SeeNet v 2.4.12 (20.10.2020). A specially crafted HTTP request can lead to arbitrary PHP code execution. An attacker can send a crafted HTTP request to trigger this vulnerability.
How severe is CVE-2021-21804?: CVE-2021-21804 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-2021-21804 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (88th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21804?: CVE-2021-21804 affects Advantech R-seenet. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-21804?: 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-2021-21804 published?: CVE-2021-21804 was published on 2021-07-16 and last updated on 2026-06-17.

References

https://talosintelligence.com/vulnerability_reports/TALOS-2021-1273

Affected products (1)

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

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