How severe is CVE-2021-28840?

CVE-2021-28840 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-28840 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-28840?

CVE-2021-28840 primarily affects Dlink Dap-2310 Firmware. In total, 9 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-28840?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-28840 published?

CVE-2021-28840 was published on 2021-08-10 and last updated on 2026-06-17.

CVE-2021-28840

CVE-2021-28840 is a high-severity vulnerability in Dlink Dap-2310 Firmware with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-476.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 2% (81st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-476
Affected product: Dlink Dap-2310 Firmware
Published: 2021-08-10
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-28840?: 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.
How severe is CVE-2021-28840?: CVE-2021-28840 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-28840 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-28840?: CVE-2021-28840 primarily affects Dlink Dap-2310 Firmware. In total, 9 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-28840?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-28840 published?: CVE-2021-28840 was published on 2021-08-10 and last updated on 2026-06-17.

References

Affected products (9)

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

More vulnerabilities in Dlink Dap-2310 Firmware

CVE-2016-1558 — Critical (CVSS 9.8): Buffer overflow in D-Link DAP-2310 2.06 and earlier, DAP-2330 1.06 and earlier, DAP-2360 2.06 and earlier, DAP-2553 H/W…
CVE-2022-38873 — High (CVSS 7.5): D-Link devices DAP-2310 v2.10rc036 and earlier, DAP-2330 v1.06rc020 and earlier, DAP-2360 v2.10rc050 and earlier,…
CVE-2021-28839 — High (CVSS 7.5): Null Pointer Dereference vulnerability exists in D-Link DAP-2310 2.07.RC031, DAP-2330 1.07.RC028, DAP-2360 2.07.RC043,…
CVE-2021-28838 — High (CVSS 7.5): Null pointer dereference vulnerability in D-Link DAP-2310 2,10RC039, DAP-2330 1.10RC036 BETA, DAP-2360 2.10RC055,…

All CVEs affecting Dlink Dap-2310 Firmware →

Other CWE-476 (NULL Pointer Dereference) vulnerabilities

CVE-2022-36648 — Critical (CVSS 10.0): The hardware emulation in the of_dpa_cmd_add_l2_flood of rocker device model in QEMU, as used in 7.0.0 and earlier,…
CVE-2020-14500 — Critical (CVSS 10.0): Secomea GateManager all versions prior to 9.2c, An attacker can send a negative value and overwrite arbitrary data.
CVE-2010-2495 — Critical (CVSS 10.0): The pppol2tp_xmit function in drivers/net/pppol2tp.c in the L2TP implementation in the Linux kernel before 2.6.34 does…
CVE-2026-46195 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: smb: client: validate dacloffset before building…
CVE-2026-31657 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: batman-adv: hold claim backbone gateways by…
CVE-2026-31436 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: dmaengine: idxd: fix possible wrong descriptor…

Browse all CWE-476 (NULL Pointer Dereference) vulnerabilities →