CVE-2021-28843Network attack vector

Service crash via unknown apply_cgi action

Published Aug 10, 2021 · Updated Aug 3, 2024

Null pointer dereference in TRENDnet TEW access-point firmware 1.11B03 allows remote attackers to crash affected devices. The TEW-755AP, TEW-755AP2KAC, TEW-821DAP2KAC, and TEW-825DAP apply_cgi handler fails to reject an unknown POST action name before dereferencing a null pointer. The request requires no credentials or user interaction; the documented consequence is remotely triggered availability loss, not data access or modification.

CVSS severity7.5
High
EPSS probability0.96%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Null pointer dereference in TRENDnet TEW access-point firmware 1.11B03 allows remote attackers to crash affected devices. The TEW-755AP, TEW-755AP2KAC, TEW-821DAP2KAC, and TEW-825DAP apply_cgi handler fails to reject an unknown POST action name before dereferencing a null pointer. The request requires no credentials or user interaction; the documented consequence is remotely triggered availability loss, not data access or modification.

The record

CVE
CVE-2021-28843
Published
Aug 10, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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