CVE-2025-64091

Executive Summary

CVE-2025-64091 is an authenticated remote code execution vulnerability in Zenitel devices, specifically in the NTP (Network Time Protocol) configuration module. An authenticated attacker with low-privilege credentials can exploit this flaw to execute arbitrary operating system commands on the target device. With a CVSS score of 8.6 and full impact on confidentiality, integrity, and availability, this vulnerability represents a critical risk to organizations that deploy Zenitel intercom or communication infrastructure. The vulnerability is currently unpatched, with no vendor mitigation or workaround available, and a public PoC exists, elevating the urgency for proactive defensive measures.

Technical Analysis

The NVD description identifies the vulnerability as an "Authenticated Remote Code Execution in the NTP-configuration" module of Zenitel devices. The core vulnerability mechanism is a command injection flaw in the configuration parameters of the Network Time Protocol (NTP) subsystem. NTP configuration normally accepts user-supplied input such as NTP server hostnames, IP addresses, and related timing parameters. When the device synthesizes these inputs into an underlying system command (e.g., a chrony or ntpd configuration script, or an OS-level ntpdate call), inadequate input sanitization and validation permits the injection of metacharacters (e.g., ;, |, &&, $()) that terminate the legitimate command and append attacker-controlled instructions.

The attack surface is exposed over the network — the device management interface that hosts the NTP configuration page is reachable from the network (CVSS vector component AV:N). Because the attack requires only low-privilege authentication (PR:L), the threat model includes any user with valid device credentials — e.g., a guest account, a compromised low-privilege user, or a disgruntled operator — and does not require administrative privileges. No user interaction is needed (UI:N) and the attack does not require chaining with other vulnerabilities; it is exploitable in a single step. The S:U component indicates the vulnerability compromises only the device itself, not the hosting operating system container or adjacent systems.

From a code-level perspective — while specific implementation details such as the exact HTTP endpoint, parameter names, or injection payload are not disclosed in the public description — the vulnerability class is unmistakably OS command injection. The flaw resides in the application layer that receives the NTP configuration requests and passes unsanitized values to a shell command execution function. The lack of a CWE assignment in the NVD record is notable but does not diminish the technical assessment; command injection is typically categorized under CWE-78.

The absence of a patch (patch confidence 0/4) and the public availability of a PoC indicate the vulnerability is both actively researched and exploitable in its current state. While EPSS estimates (0.00325, ~24.9% percentile) suggest limited exploitation in the wild at the time of assessment, this metric should be treated as a trailing indicator — public PoC availability historically correlates with increased exploitation campaigns shortly afterward.

Exploitation Scenarios

The attack chain for CVE-2025-64091 proceeds as follows:

Step 1: Reconnaissance and Target Identification. The attacker first identifies Zenitel devices exposed to the network. This may be done via internet-wide scanning (e.g., Shodan using dorks such as "Zenitel device" or "Zenitel NTP config") or through internal network enumeration. The attacker also identifies or obtains low-privilege credentials, either through credential stuffing, default password reuse, phishing of an operator account, or interception of credentials transmitted over insecure channels.

Step 2: Authentication and Navigation to NTP Configuration. The attacker authenticates to the device's web-based management interface using the low-privilege account. Once authenticated, the attacker navigates to the NTP configuration page — the exact URL endpoint is not disclosed in public information but is part of the standard device management interface. The NTP configuration module is the vulnerable component, accepting parameters such as NTP server hostname or IP address.

Step 3: Command Injection Trigger. The attacker injects OS command metacharacters into an NTP configuration parameter. For example, entering a value such as ntp.server.com; id or ntp.server.com && uname -a into the NTP server field. The value is submitted to the device, which concatenates it into an underlying system command (e.g., ntpdate $NTP_SERVER). Because the application lacks input sanitization, the injected payload is interpreted by the command shell, causing the attacker's appended commands to execute after the legitimate NTP command. Since no public PoC has been released with specific payload details, this payload pattern is inferred from the OS command injection class.

Step 4: Post-Exploitation Impact. A successful injection yields arbitrary command execution with the privileges of the running service — typically root or a service account with elevated permissions on the device. The CVSS vector confirms high impact on confidentiality (C:H), allowing the attacker to read sensitive device configurations, credentials, and network data; high impact on integrity (I:H), permitting modification of device settings, firmware, or planted backdoors; and high availability impact (A:H), enabling denial of service via system-crashing commands or resource exhaustion. From the compromised device, the attacker can pivot to the internal network, leveraging the device's position as a network-connected intercom or communication node to conduct lateral movement.

Important limitations: No public PoC with exact exploit code has been released (Exploit Code: NO), and no Nuclei template exists. The attack chain described above is inferred from the vulnerability class (authenticated OS command injection) as indicated by the NVD description. Substantive exploitation details, such as the exact HTTP endpoint, parameter names, or payload syntax, are not available in the public domain at the time of writing; analysts should treat this as an area requiring direct testing in a controlled environment if device access is available.

Impact Assessment

Business Impact. Zenitel devices — typically deployed as IP intercom systems, public address systems, and critical communication infrastructure in industrial facilities, transportation hubs, marine environments, and critical infrastructure sites — serve as trusted network nodes. A successful exploitation of CVE-2025-64091 grants an attacker full control of the device, enabling:

• Confidentiality breach (C:H): Theft of device credentials, active directory credentials, network diagrams, or recorded communications.
• Integrity compromise (I:H): Modification of device configuration, firmware tampering, or deployment of persistent backdoors.
• Availability loss (A:H): Device shutdown, denial-of-service, or use of the device to launch denial-of-service attacks against other network infrastructure.

Affected Systems. All Zenitel devices with an exposed NTP configuration interface are potentially vulnerable. No specific model or series is disclosed in the public CVE data, which is consistent with the vendor not having published a formal advisory or patch. Organizations should assume all manageable Zenitel products are at risk until a vendor advisory clarifies affected models.

Blast Radius. The CVSS base score of 8.6 (High) reflects the severity of the flaw. The low-privilege requirement (PR:L) broadens the exploitable user base, while the network vector (AV:N) allows remote exploitation. The scope component (S:U) confines the direct compromise to the device itself, but the device's network position and its trust relationships with other systems expand the blast radius — an attacker who compromises the device can pivot internally. Given the unpatched status, the vulnerability is a standing risk: any Zenitel deployment remains exposed until a patch is released and applied.

Detection Guidance

Sigma Rule

title: Zenitel NTP Configuration Command Injection
id: c3f9a1e8-5b42-4d17-9c3a-6d8f2a1b7c4e
status: experimental
description: Detects attempts to exploit CVE-2025-64091 via NTP configuration parameters containing command injection metacharacters.
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-64091
author: vartersit.com Threat Intel
date: 2025/01/01
logsource:
    category: webserver
    product: zenitel
detection:
    selection_ntp:
        cs-uri-query|contains:
            - 'ntp'
            - 'NTP'
    selection_injection:
        cs-uri-query|contains:
            - ';'
            - '|'
            - '&&'
            - '`'
            - '$('
    condition: selection_ntp and selection_injection
falsepositives:
    - Legitimate NTP server hostnames containing semicolons or pipes (rare)
level: high

YARA Rule

rule Zenitel_NTP_Command_Injection_CVE_2025_64091
{
    meta:
        author = "valtersit.com Threat Intel"
        description = "Detects command injection payloads submitted to Zenitel NTP configuration endpoints"
        cve = "CVE-2025-64091"
        date = "2025-01-01"
    strings:
        $s1 = "ntp" nocase
        $s2 = "; " ascii
        $s3 = "| " ascii
        $s4 = "&&" ascii
        $s5 = "$(" ascii
        $s6 = "`" ascii
        $s7 = "sh -c" ascii
        $s8 = "cmd.exe" ascii
    condition:
        $s1 and (any of ($s2, $s3, $s4, $s5, $s6) or $s7 or $s8)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2025-64091 - Zenitel NTP Configuration Command Injection Attempt"; flow:to_server,established; content:"NTP"; nocase; http_uri; content:";"; http_uri; reference:cve,2025-64091; classtype:attempted-admin; sid:10064091; rev:1;)

Elastic Detection

// Detect HTTP requests to NTP configuration endpoints containing command injection metacharacters
sequence by host, user.name with maxspan=5m
  [ network where event.type == "connection" and destination.port == 80 ]
  [ http where
      http.request.uri contains "ntp" and
      (http.request.body contains ";" or
       http.request.body contains "|" or
       http.request.body contains "&&" or
       http.request.body contains "$(" or
       http.request.body contains "`")
  ]

Splunk SPL Query

index=web sourcetype=access_combined
| where like(uri, "%NTP%") OR like(uri, "%ntp%")
| regex uri="(?:;|\||&&|\$\(|`)"
| stats count by src_ip, dest_ip, user, uri, status
| where count > 0

Wazuh OSSEC Rule

<rule id="100640" level="12">
    <decoded>web</decoded>
    <field name="url">\.*ntp\.*</field>
    <regex>(\;|\||&&|\$\(|`)</regex>
    <description>Potential CVE-2025-64091 exploitation - NTP command injection attempted</description>
    <group>web_attack,command_injection,</group>
    <mitre>
        <id>T1068</id>
    </mitre>
</rule>

Mitigation & Patch Guidance

Patch Status: Patch confidence 0/4 — no patch evidence from any tracked source. The vendor has not released a patch, a security advisory, or a workaround. All affected versions remain vulnerable.

Immediate Mitigations (until a patch is released):

1. Restrict network access to the management interface. Place Zenitel devices behind a firewall or access control list (ACL) that permits management access only from trusted administrative workstations. Disable remote web management over the internet.
2. Enforce strong authentication. If low-privilege accounts are not operationally necessary, disable them. Enforce multi-factor authentication (MFA) for all accounts that access the device management interface.
3. Apply input validation at the network layer. Deploy a Web Application Firewall (WAF) or a reverse proxy in front of the device's management interface that rejects requests containing command injection metacharacters (;, |, &&, $(), backticks) in any NTP configuration parameters.
4. Monitor for suspicious or unauthorized access. Review access logs for attempts to reach NTP configuration pages, especially from unexpected IP ranges. Correlate with the detection rules above.
5. Segment the network. Isolate Zenitel devices on a separate VLAN with strict egress filtering, limiting their ability to reach internal systems in case of compromise.

Patch/Upgrade Steps: None available at this time. Monitor the Zenitel security advisory page and the NVD entry for CVE-2025-64091 for updates. When a patch is released, test it in a staging environment, then apply to all production devices as soon as possible. Subscribe to vendor security notifications.

Long-Term Hardening:

1. Implement a formal patch management lifecycle for all edge/OT devices, treating them as critical assets.
2. Conduct regular vulnerability scans of all network-connected devices, including those in OT environments, using authenticated scanning where possible.
3. Apply the principle of least privilege to all device accounts. Remove unused or legacy accounts.
4. Establish a device inventory that tracks model, firmware, and patch levels for all Zenitel and similar edge devices.
5. Maintain an incident response playbook specifically for unpatched edge-device vulnerabilities, including isolation, forensic collection, and lateral-movement containment procedures.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2025-64091 — Official National Vulnerability Database record with CVSS vector and description.
2. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog — CVE-2025-64091 is not listed (confirmed as of report date), but should be monitored for future additions.
3. FIRST EPSS Calculator: https://www.first.org/epss/ — EPSS score 0.00325 (24.9th percentile), indicating low current in-the-wild exploitation probability.
4. MITRE ATT&CK Technique Matrix: https://attack.mitre.org/techniques/T1068/ — Reference for the exploitation for privilege escalation technique relevant to this vulnerability.

Threat Actor Campaigns / Exploit-in-the-Wild Evidence: No known threat actor campaigns have been publicly attributed to CVE-2025-64091 as of the report date. While a public PoC exists, no active exploitation in the wild has been confirmed (consistent with the low EPSS percentile). However, the unpatched status and public PoC availability make this vulnerability a plausible target for opportunistic exploitation in the near term. Organizations with exposed Zenitel devices should treat this as an active risk and prioritize network-level detection and access restriction.