Is CVE-2021-21805 actively exploited?

Yes. CVE-2021-21805 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, which means exploitation in the wild has been confirmed.

Can CVE-2021-21805 be exploited remotely?

The attack vector of CVE-2021-21805 has not been classified yet.

What is the CVSS score of CVE-2021-21805?

CVE-2021-21805 has not received a CVSS score yet.

HOME VULNERABILITIESCVE-2021-21805

UNKNOWNCISA KEVIN THE WILD

CVE-2021-21805

Published: April 11, 2026

EPSS:92.87%probability of exploitation in 30 daysPercentile:99.8th

Official 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.

NVD Source

Technical Analysis

CVE-2021-21805 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

CISA has added CVE-2021-21805 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.