CVE-2021-28840

Exp

Null Pointer Dereference vulnerability exists in D-Link DAP-2310 2.07.RC031, DAP-2330 1.07.RC028, DAP-2360 2.07.RC043, DAP-2553 3.06.RC027, DAP-2660 1.13.RC074, DAP-2690 3.16.RC100, DAP-2695 1.17.RC063, DAP-3320 1.01.RC014 and DAP-3662 1.01.RC022 in the upload_config function of sbin/httpd binary. When the binary handle the specific HTTP GET request, the content in upload_file variable is NULL in the upload_config function then the strncasecmp would take NULL as first argument, and incur the NULL pointer dereference vulnerability.

Published: 2021-08-10 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-28840 is rated High Exploit Risk (70.8/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.04%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-28840

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-28840

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-03-30 1.63% 1.04% -0.59%
2 2025-03-29 1.04% 1.63% +0.59%
3 2025-03-17 — 1.04% —

Full EPSS history (9 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-28840

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-28840

Affected software / configurations for CVE-2021-28840

Vendor Product Version Raw CPE
dlink dap-2310_firmware 2.0.7.rc031 cpe:2.3:o:dlink:dap-2310_firmware:2.0.7.rc031:*:*:*:*:*:*:*
dlink dap-2330_firmware 1.07.rc028 cpe:2.3:o:dlink:dap-2330_firmware:1.07.rc028:*:*:*:*:*:*:*
dlink dap-2360_firmware 2.07.rc043 cpe:2.3:o:dlink:dap-2360_firmware:2.07.rc043:*:*:*:*:*:*:*
dlink dap-2553_firmware 3.06.rc027 cpe:2.3:o:dlink:dap-2553_firmware:3.06.rc027:*:*:*:*:*:*:*
dlink dap-2660_firmware 1.13.rc074 cpe:2.3:o:dlink:dap-2660_firmware:1.13.rc074:*:*:*:*:*:*:*
dlink dap-2690_firmware 3.16.rc100 cpe:2.3:o:dlink:dap-2690_firmware:3.16.rc100:*:*:*:*:*:*:*
dlink dap-2695_firmware 1.17.rc063 cpe:2.3:o:dlink:dap-2695_firmware:1.17.rc063:*:*:*:*:*:*:*
dlink dap-3320_firmware 1.01.rc014 cpe:2.3:o:dlink:dap-3320_firmware:1.01.rc014:*:*:*:*:*:*:*
dlink dap-3662_firmware 1.01.rc022 cpe:2.3:o:dlink:dap-3662_firmware:1.01.rc022:*:*:*:*:*:*:*

References for CVE-2021-28840

cvelogic Threat Intelligence