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CVE-2021-28839

22
FAUCET Score

CVE-2021-28839 is a Null Pointer Dereference vulnerability affecting multiple D-Link DAP series access points, including models like the DAP-2310, DAP-2330, and DAP-2690. This flaw resides in the upload_certificate function of the sbin/httpd binary, triggered when a specific HTTP GET request causes the strrchr function to receive a NULL argument. Rated 7.5 HIGH on the CVSS scale, it presents a network-based attack with low complexity, requiring no user interaction or privileges, and can lead to high availability impact. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
2.0.7.rc031CPE matchmatch criteria
cpe:2.3:o:dlink:dap-2310_firmware:2.0.7.rc031:*:*:*:*:*:*:*
1.07.rc028CPE matchmatch criteria
cpe:2.3:o:dlink:dap-2330_firmware:1.07.rc028:*:*:*:*:*:*:*
2.07.rc043CPE matchmatch criteria
cpe:2.3:o:dlink:dap-2360_firmware:2.07.rc043:*:*:*:*:*:*:*
3.06.rc027CPE matchmatch criteria
cpe:2.3:o:dlink:dap-2553_firmware:3.06.rc027:*:*:*:*:*:*:*
1.13.rc074CPE matchmatch criteria
cpe:2.3:o:dlink:dap-2660_firmware:1.13.rc074:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.38%
Probability of exploitation in next 30 days
EPSS Percentile
69.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0138 is in the 50th percentile among its peer group of 51,485 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

github.com / zyw-200/EQUAFL/blob/main/dlink-email-cve2.pdf
Third Party Advisory
github.com / zyw-200/EQUAFL/blob/main/dlink-email-cve.pdf
ExploitThird Party Advisory
dlink.com / en/security-bulletin
Vendor Advisory