CVE-2023-23328Public exploitNetwork attack vector

Authenticated code execution via MIME-only upload validation

Published Mar 10, 2023 · Updated Jul 9, 2026

Arbitrary file upload in AvantFAX 3.3.7 allows remote authenticated users to execute code through the Send Fax document upload. The load_file() function in includes/FileUpload.php trusts mime_content_type() output while leaving a .php extension unchecked, so prefixed text makes PHP content appear as allowed text/plain. Any authenticated low-privilege account can place the file under the web-accessible /avantfax/tmp directory; predictable time-based filename prefixes then expose a web shell that runs commands as the web server user.

CVSS severity8.8
High
EPSS probability1.02%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Arbitrary file upload in AvantFAX 3.3.7 allows remote authenticated users to execute code through the Send Fax document upload. The load_file() function in includes/FileUpload.php trusts mime_content_type() output while leaving a .php extension unchecked, so prefixed text makes PHP content appear as allowed text/plain. Any authenticated low-privilege account can place the file under the web-accessible /avantfax/tmp directory; predictable time-based filename prefixes then expose a web shell that runs commands as the web server user.

The record

CVE
CVE-2023-23328
Published
Mar 10, 2023
Updated
Jul 9, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-434, T1190, T1505.003
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 10, 2023CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 2026Record 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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
8.8NVDCVSS:3.1/AV:N/AC:L/PR:L/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.

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

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type
T1190Exploit Public-Facing Application
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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