What it is
CVE-2021-39509 is an unauthenticated vulnerability affecting D-Link DIR-816. An issue was discovered in D-Link DIR-816 DIR-816A2_FWv1.10CNB05_R1B011D88210 The HTTP request parameter is used in the handler function of...
Vulnerability report
Exploited in the wild
High confidence
Not in CISA KEV
CVE-2021-39509
DIR-816 Command Injection
D-Link / DIR-816
- Severity
- CVSS 9.8 · Critical
- Confidence
- High
- Exploit status
- Exploited in the wild
- EPSS
- 5.1%
- First observed
- —
- Last observed
- —
Decision summary
What security teams need to know first
Direct answers before the deeper technical record.
Is it exploited?
Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is high.
Who is affected?
D-Link / DIR-816.
What should we do?
Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
Overview
DIR-816 Command Injection
An issue was discovered in D-Link DIR-816 DIR-816A2_FWv1.10CNB05_R1B011D88210 The HTTP request parameter is used in the handler function of /goform/form2userconfig.cgi route, which can construct the user name string to delete the user function.
This can lead to command injection through shell metacharacters.
- Published
- 24 Aug 2021
- Exploitation Reported
- 24 Aug 2021
- Attack vector
- Remote
- Complexity
- Low
- Privileges
- None
- User interaction
- None
CVE References
- CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2021-39509
- dlink.com/en/security-bulletin dlink.com · CVE Record https://www.dlink.com/en/security-bulletin/
- GitHub — doudoudedi/main-DIR-816_A2_Command-injection github.com · CVE Record https://github.com/doudoudedi/main-DIR-816_A2_Command-injection/blob/...
- GitHub — doudoudedi/main-DIR-816_A2_Command-injection github.com · CVE Record https://github.com/doudoudedi/main-DIR-816_A2_Command-injection
Exploitation evidence
Why KEV Intelligence marks this CVE as exploited
Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.
Exploited in the wild
The Shadowserver
Independent exploitation attestation added to the KEV Intelligence record.
Known exploited vulnerability sources
Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.
Learn about Pro API access| Source | Added |
|---|---|
| The Shadowserver First | 2021-08-24 18:52 UTC |
Detection
Operational artifacts and observed signals
Make the evidence actionable in scanner, SOC, and edge-control workflows.
Observed signals
- Request targets
- 0
- User-Agents
- 0
Raw values available in Pro and Enterprise.
Scanner coverage
No scanner integrations recorded yet.
Virtual patch status
No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.
Learn about virtual patches →No detection artifacts or sensor request patterns are available for this CVE yet.
Check back as sensor telemetry and scanner integrations are updated.
Risk and context
Severity, weaknesses, and research context
CVSS v3.1
9.8
Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
5.1%
All CVSS Scores
CVSS v3.1
9.8
Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v2.0
7.5
High
AV:N/AC:L/Au:N/C:P/I:P/A:P
Timeline
From disclosure to observed exploitation
-
Added to KEV Intelligence KEV Feed
High-confidence, third-party attested exploitation
-
CVE published
Vulnerability disclosed publicly
-
CVE ID reserved
Identifier reserved by the CNA
Pro API
Automate this intelligence
Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
- Evidence confidence and provenance
- First-party sensor telemetry
- PoC and scanner references
- Affected versions and enrichment
- Automation-ready JSON delivery
GET /api/v2/pro/kevs/CVE-2021-39509
Free JSON includes basic KEV fields{
"cve_id": "CVE-2021-39509",
"confidence": "High",
"cvss_score": 9.8,
"cvss_estimated": false,
"epss_score": 0.05098,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "attempts": 0, "sensors": 0 }
}Early warning alerts
Get alerts on high-impact exploitation
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