CVE-2025-34335

HighPublic PoCRCE

Published: 19 November 2025

Published

19 November 2025

Modified

11 December 2025

KEV Added

—

Patch

—

CVSS Score 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0066 71.2th percentile

Risk Priority 18 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2025-34335 is a high-severity OS Command Injection (CWE-78) vulnerability in Audiocodes Fax Server. Its CVSS base score is 8.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 28.8% 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 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 2 other techniques. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-10 Information Input Validation good match

prevent

SI-10 requires validation of inputs like filename extensions at upload points to block shell metacharacters from being injected into command strings executed by exec().

SI-2 Flaw Remediation good match

prevent

SI-2 mandates timely identification, reporting, and correction of flaws such as this command injection vulnerability through patching affected AudioCodes appliances.

SI-4 System Monitoring partial match

detect

SI-4 enables monitoring of system activities to detect indicators of command injection attacks, such as anomalous executions of fax_server_lic_cmdline.exe.

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 →

T1059.003 Windows Command Shell Execution

Adversaries may abuse the Windows command shell for execution.

attack.mitre.org →

T1068 Exploitation for Privilege Escalation Privilege Escalation

Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.

attack.mitre.org →

Why these techniques?

Authenticated command injection in a network-accessible web interface (license upload) enables exploitation of public-facing application (T1190), Windows command shell execution via shell metacharacters (T1059.003), and privilege escalation from authenticated user to NT AUTHORITY\SYSTEM (T1068).

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 expose an authenticated command injection vulnerability in the license activation workflow handled by AudioCodes_files/ActivateLicense.php. When a license file is uploaded, the application derives a new filename by…

combining a generated base name with the attacker-controlled extension portion of the original upload name, then constructs a command line for fax_server_lic_cmdline.exe that includes this path. The extension value is incorporated into the command string without input validation, escaping, or proper argument quotation before being passed to exec(). An authenticated user with access to the license upload interface can supply a specially crafted filename whose extension injects additional shell metacharacters, causing arbitrary commands to be executed as NT AUTHORITY\\SYSTEM.

Deeper analysisAI

CVE-2025-34335 is an authenticated command injection vulnerability (CWE-78) in AudioCodes Fax Server and Auto-Attendant IVR appliances, affecting versions up to and including 2.6.23. The flaw occurs in the license activation workflow managed by AudioCodes_files/ActivateLicense.php. During license file upload, the application generates a new filename by combining a base name with the attacker-controlled extension from the original filename. This path is then incorporated without input validation, escaping, or proper quotation into a command string passed to exec() for fax_server_lic_cmdline.exe.

An authenticated user with access to the license upload interface can exploit this by supplying a specially crafted filename extension containing shell metacharacters. This injects and executes arbitrary commands as NT AUTHORITY\SYSTEM. The vulnerability has a CVSS v3.1 base score of 8.8 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H), enabling network-accessible attacks with low complexity and privileges required, resulting in high impacts to confidentiality, integrity, and availability.

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