CVE-2021-21805
High PUBLISHEDAn 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...
Not yet in CISA KEV
Recommended Action
Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
At a Glance
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.
- CVE Published
- Aug 05, 2021
- Exploitation Reported
- Jun 06, 2026
- CVSS
- 9.8 Critical
- EPSS
- 69.6%
Affected Versions
| Vendor | Product | Version | Status |
|---|---|---|---|
| n/a |
Advantech
|
Advantech R-SeeNet 2.4.12 (20.10.2020) |
Affected |
CVE References
- talosintelligence.com/vulnerability_reports/TALOS-2021-1274 talosintelligence.com · CVE Record https://talosintelligence.com/vulnerability_reports/TALOS-2021-1274
Recommended Actions
- Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
- Check enrichment artifacts for scanner coverage and available PoCs before rolling remediation validation.
- Use the Pro API to automate enrichment, telemetry, and workflow delivery for VM, SOC, and CTI pipelines.
Known Exploited Vulnerability Sources
Catalogues that list this CVE as a known exploited vulnerability.
Per-source evidence links for KEV attestations are available through the KEVIntel Pro API.
Learn about Pro API access| Source | Added |
|---|---|
| The Shadowserver First | 2026-06-06 00:00 UTC |
Scanner Artifacts
Nuclei and Metasploit references linked to this CVE.
| Scanner | Reference | Detected |
|---|---|---|
| Nuclei | https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-21805.yaml | Apr 25, 2025 |
Virtual Patch
Compensating WAF rules to help reduce exposure to this CVE. Rule content and deployable vendor exports are available with KEVIntel Enterprise.
KEVIntel does not currently have a virtual patch for this CVE. When available, KEVIntel virtual patches ship as deployable ModSecurity, Cloudflare, and AWS WAF rules.
Enterprise feature. Virtual patch rule content and deployable vendor exports (ModSecurity, Cloudflare, AWS WAF) are available to KEVIntel Enterprise users.
CVSS Scores
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
AV:N/AC:L/Au:N/C:C/I:C/A:C
Exploitation Status
Exploited in the wild
Recorded 2026-06-06 00:00:00 UTC · The Shadowserver
Proof of concept available
Recorded 2026-06-12 14:20:19 UTC · Nuclei Templates
Weaknesses (CWE)
-
Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Scanner Integrations
| Scanner | Reference | Detected |
|---|---|---|
| Nuclei | https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-21805.yaml | Apr 25, 2025 |
Potential Proof of Concepts
These PoCs are unverified and could contain malware. Use at your own risk.
nuclei · Created Unknown
Timeline
Key exploitation, disclosure, scanner coverage, and KEV attestation events for this CVE.
-
14:20 UTC about 1 month ago14:20 UTC · about 1 month ago
Public PoC available
Public proof-of-concept code published
-
00:00 UTC about 1 month ago00:00 UTC · about 1 month ago
Added to KEVIntel KEV Feed
High-confidence, third-party attested exploitation
-
00:00 UTC about 1 year ago00:00 UTC · about 1 year ago
Nuclei template available
Scanner coverage available
-
20:03 UTC almost 5 years ago20:03 UTC · almost 5 years ago
CVE published
Vulnerability disclosed publicly
-
00:00 UTC over 5 years ago00:00 UTC · over 5 years ago
CVE ID reserved
Identifier reserved by the CNA
Automate This Intelligence with the Pro API
Confidence scoring, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
Pro API Example
GET /api/v2/pro/kevs/CVE-2021-21805
{
"cve_id": "CVE-2021-21805",
"title": "An OS Command Injection vulnerability exists in the ping.php script functiona...",
"affected_vendor": "Advantech",
"affected_product": "R-SeeNet",
"affected_versions": [
{ "vendor": "...", "product": "...", "status": "affected", "display_label": "..." }
],
"confidence": "High",
"cvss_score": 9.8,
"epss_score": 0.69631,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "...": "Pro API fields" },
"proof_of_concepts": [ "..." ],
"scanner_integrations": [ "..." ]
}