CVE-2021-35290Public exploitNetwork attack vector

Authenticated code execution via extension parsing flaw

Published Feb 24, 2023 · Updated Mar 12, 2025

Unrestricted file upload in Balero CMS 0.8.3 allows remote authenticated users to execute arbitrary code through the blog editor. Uploader.php takes the second dot-delimited segment of an uploaded filename as its extension and moves the file into public/images without validating its type, so shell.php.jpg is stored with a .php extension. Administrator access to /admin/main/mod-blog is required, after which the uploaded web shell executes commands in the web server's context.

CVSS severity7.2
High
EPSS probability0.93%
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 Balero CMS 0.8.3 allows remote authenticated users to execute arbitrary code through the blog editor. Uploader.php takes the second dot-delimited segment of an uploaded filename as its extension and moves the file into public/images without validating its type, so shell.php.jpg is stored with a .php extension. Administrator access to /admin/main/mod-blog is required, after which the uploaded web shell executes commands in the web server's context.

The record

CVE
CVE-2021-35290
Published
Feb 24, 2023
Updated
Mar 12, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-434, T1505.003
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Feb 24, 2023CVE publishedPublication date reported by the CVE source.
  2. Mar 12, 2025Record 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

7.2NIST NVDCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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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