Security readout for executives and security teams
Plain-English summary
Certain D-Link DAP wireless access points can crash or malfunction when their web management service handles a particular certificate-upload related HTTP request. The public record identifies a null pointer dereference, but does not provide a CVSS score, confirmed exploitation, or a specific vendor fix in the provided sources.
Executive priority
Treat this as an exposure-control issue until vendor guidance is confirmed. Prioritize sites where wireless access point management is reachable outside trusted admin networks.
Technical view
CVE-2021-28839 is a null pointer dereference in upload_certificate within the sbin/httpd binary. For listed D-Link DAP firmware versions, handling a specific HTTP GET request can cause strrchr to receive NULL as its first argument, triggering the fault.
Likely exposure
Exposure is most relevant where affected D-Link DAP access points run the listed firmware and their HTTP management interface is reachable by untrusted users, guest networks, or the internet.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation. It states a specific HTTP GET request can trigger the condition, which suggests availability risk if the management web service is reachable.
Researcher notes
The record identifies the vulnerable function and binary, but the provided sources lack CVSS, CWE mapping, patch details, and exploit confirmation. Avoid assuming impact beyond likely denial of service from null pointer dereference.
Mitigation direction
- Inventory D-Link DAP models and firmware versions listed in the CVE record.
- Check D-Link security guidance for applicable firmware updates or vendor-directed actions.
- Restrict web management access to trusted admin networks or VPN only.
- Disable internet exposure of access point management interfaces where possible.
- Monitor affected devices for unexplained web service failures or reboots.
Validation and detection
- Confirm whether listed DAP models exist in asset inventory.
- Verify deployed firmware against the vulnerable versions in the CVE description.
- Review perimeter and internal firewall rules for management HTTP exposure.
- Check management logs for unusual certificate-upload related web requests, if logs are available.
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.
CVE-2021-28839 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
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/zyw-200/EQUAFL/blob/main/dlink-email-cve.pdfCVE reference · x_refsource_MISC
- https://github.com/zyw-200/EQUAFL/blob/main/dlink-email-cve2.pdfCVE 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.