CVE-2025-34328

CriticalPublic PoC

Published: 19 November 2025

Published

19 November 2025

Modified

12 December 2025

KEV Added

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Patch

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CVSS Score 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0053 67.6th percentile

Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2025-34328 is a critical-severity Unrestricted Upload of File with Dangerous Type (CWE-434) vulnerability in Audiocodes Fax Server. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 32.4% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified are NIST 800-53 AC-3 (Access Enforcement) and AC-6 (Least Privilege).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190). What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

AC-3 Access Enforcement good match

prevent

Enforces access controls to block unauthenticated remote access to the vulnerable script-management endpoint at ajaxScript.php.

SI-10 Information Input Validation good match

prevent

Requires validation of attacker-supplied data before writing to server-side files, directly addressing the unrestricted arbitrary file write vulnerability.

AC-6 Least Privilege good match

prevent

Restricts web service account privileges below NT AUTHORITY\SYSTEM to limit impact of arbitrary file writes and subsequent code execution.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

Why these techniques?

The vulnerability is an unauthenticated arbitrary file write in a public-facing web administration component, enabling remote code execution, which directly maps to exploitation of public-facing applications.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

NVD Description

AudioCodes Fax Server and Auto-Attendant IVR appliances versions up to and including 2.6.23 include a web administration component (F2MAdmin) that exposes an unauthenticated script-management endpoint at AudioCodes_files/utils/IVR/diagram/ajaxScript.php. The saveScript action writes attacker-supplied data directly to a server-side file path under…

the privileges of the web service account, which runs as NT AUTHORITY\\SYSTEM on Windows deployments. A remote, unauthenticated attacker can write arbitrary files into the product’s web-accessible directory structure and subsequently execute them.

Deeper analysisAI

CVE-2025-34328 is an unauthenticated arbitrary file write vulnerability in AudioCodes Fax Server and Auto-Attendant IVR appliances, affecting versions up to and including 2.6.23. The issue exists in the F2MAdmin web administration component, which exposes a script-management endpoint at AudioCodes_files/utils/IVR/diagram/ajaxScript.php. The saveScript action writes attacker-supplied data directly to a server-side file path under the privileges of the web service account, which runs as NT AUTHORITY\SYSTEM on Windows deployments.

A remote, unauthenticated attacker can exploit this endpoint to write arbitrary files into the product's web-accessible directory structure and subsequently execute them, resulting in remote code execution with SYSTEM-level privileges. The vulnerability has a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) and is categorized under CWE-434 (Unrestricted Upload of File with Dangerous Type).

Advisories from Pierre Kim and VulnCheck provide technical details on the vulnerability, including proof-of-concept exploitation. AudioCodes has issued a product notice announcing end-of-service for the Auto-Attendant IVR solution.