CVE-2021-43100Public exploitNetwork attack vector

Administrator code execution via extension-blind upload validation

Published Mar 28, 2022 · Updated Aug 4, 2024

Unrestricted file upload in diyhi bbs 5.3 allows remote authenticated users with administrator access to execute arbitrary code. TopicManageAction passes application/octet-stream uploads to FileType.getType, which checks file-header signatures but does not enforce the supplied filename extension. An administrator can therefore upload a JSP web shell and execute arbitrary code when the server processes it.

CVSS severity7.2
High
EPSS probability1.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unrestricted file upload in diyhi bbs 5.3 allows remote authenticated users with administrator access to execute arbitrary code. TopicManageAction passes application/octet-stream uploads to FileType.getType, which checks file-header signatures but does not enforce the supplied filename extension. An administrator can therefore upload a JSP web shell and execute arbitrary code when the server processes it.

The record

CVE
CVE-2021-43100
Published
Mar 28, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-434, T1505.003
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Mar 28, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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 privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.2OSVCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type
T1505.003Web Shell

Public exploit references

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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