Security readout for executives and security teams
Plain-English summary
CVE-2021-39510 is a command injection issue reported in a D-Link DIR-816 A1 firmware build. A router management request parameter may be incorporated into a username deletion operation unsafely, allowing shell metacharacters to affect system command execution.
Executive priority
Treat this as a targeted network-edge risk. Prioritize validation if any D-Link DIR-816 A1 routers are deployed, internet-managed, or used in sensitive environments. Urgency is lower if the model is absent or management access is tightly restricted.
Technical view
The CVE describes improper handling of an HTTP request parameter in /goform/form2userconfig.cgi within the user deletion path of D-Link DIR816_A1_FW101CNB04. The parameter can influence a constructed username string and may lead to command injection through shell metacharacters.
Likely exposure
Exposure is likely limited to organizations or homes running the specified D-Link DIR-816 A1 firmware build, especially where the router administration interface is reachable from untrusted networks. The source bundle does not confirm authentication requirements or broader affected versions.
Exploitation context
The CVE is not listed as CISA KEV in the bundle, and no cited source confirms active exploitation. Public GitHub references suggest researcher disclosure material exists, but this analysis does not rely on exploit details beyond the CVE description.
Researcher notes
Key unknowns remain: CVSS, authentication requirement, exact parameter name, firmware lineage, and vendor fix status. The available CVE text supports command injection risk in a specific route, but not active exploitation or broader product impact.
Mitigation direction
- Check D-Link security advisories for affected firmware and vendor guidance.
- Inventory DIR-816 A1 devices and confirm firmware versions.
- Disable remote administration from the internet where present.
- Restrict management access to trusted administrative networks only.
- Replace unsupported devices if no vendor fix is available.
Validation and detection
- Search asset inventory for D-Link DIR-816 A1 routers.
- Confirm firmware build against DIR816_A1_FW101CNB04 references.
- Review firewall exposure for router management interfaces.
- Check logs for unexpected administrator or user-management activity.
- Verify D-Link bulletin status before declaring remediation complete.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
Execution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-39510 mapping review
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Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://www.dlink.com/en/security-bulletin/CVE reference · x_refsource_MISC
- https://github.com/doudoudedi/main-DIR-816_A1_Command-injection/blob/main/injection_A1.mdCVE reference · x_refsource_MISC
- https://github.com/doudoudedi/main-DIR-816_A1_Command-injectionCVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.