CVE-2025-15348

Executive Summary

CVE-2025-15348 is a critical deserialization vulnerability in Anritsu ShockLine, a vector network analyzer platform. The flaw resides in the parsing of CHX files, where untrusted data is deserialized without proper validation. An attacker can exploit this by convincing a user to open a malicious CHX file or visit a crafted page, leading to remote code execution (RCE) in the context of the current process. The vulnerability has a CVSS score of 7.8 (High), and no public exploit or patch is currently available. The EPSS score is 0.0%, indicating low exploitation activity in the wild, but the risk remains significant for targeted attacks.

This vulnerability is not related to any open-source package (NPM, PyPI, Go, Ruby) and is specific to the proprietary Anritsu ShockLine software. No supply chain implications are identified.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
• Base Score: 7.8 (High)
• Attack Vector (AV): Local – The attacker must deliver a malicious file or page to the user.
• Attack Complexity (AC): Low – No special conditions required.
• Privileges Required (PR): None – No authentication needed.
• User Interaction (UI): Required – The target must open the malicious file or page.
• Scope (S): Unchanged – The exploit affects only the vulnerable component.
• Confidentiality (C): High – Full data access possible.
• Integrity (I): High – Arbitrary code execution.
• Availability (A): High – Potential for denial of service or system compromise.

Threat Level: High. Although no public exploit exists, the vulnerability allows full code execution with user interaction. Targeted attacks against engineering or telecom environments are plausible.

Deep Dive & Mechanics

The vulnerability is a classic deserialization of untrusted data (CWE-502). The Anritsu ShockLine software parses CHX files, which are configuration or measurement data files. The parsing routine does not validate the serialized objects within the CHX file, allowing an attacker to inject malicious serialized data. When the software deserializes this data, it can instantiate arbitrary objects, leading to code execution.

Root Cause: Lack of input validation and use of insecure deserialization methods (likely Java or .NET binary serialization, common in such applications). The attacker can craft a CHX file containing a serialized payload that, upon deserialization, executes system commands or loads a remote DLL/assembly.

Attack Vector: The attacker hosts a malicious CHX file on a website or sends it via email. The user must open the file with Anritsu ShockLine. Alternatively, if the software has a web interface, the attacker could embed the file in a page that triggers automatic parsing.

Impact: Full compromise of the user's machine, including access to network analyzer data, credentials, and potential pivot points into the corporate network.

Vulnerable vs. Patched Code

Since no patch is available, a direct code comparison is not possible. However, the vulnerable code likely resembles:

// Vulnerable: Direct deserialization without type validation
object obj = new BinaryFormatter().Deserialize(stream);

A patched version would implement:

// Patched: Use safe deserialization with allowlist
var formatter = new BinaryFormatter();
formatter.Binder = new SafeBinder(); // Restrict allowed types
object obj = formatter.Deserialize(stream);

Or use JSON/XML with strict schema validation instead of binary serialization.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Anritsu ShockLine installed on a test machine.
• Ability to craft a malicious CHX file.

Steps:

1. Create a malicious serialized payload using tools like ysoserial.net (for .NET) or ysoserial (for Java), depending on the software's runtime.
2. Embed the payload into a CHX file structure. The CHX format is proprietary, but the deserialization occurs on the raw data stream, so the payload can be placed at the beginning or in a specific field.
3. Host the file on a web server or send it to the target.
4. When the target opens the file, the payload executes.

Example payload generation (conceptual):

# Using ysoserial.net for a .NET deserialization payload
ysoserial.exe -f BinaryFormatter -g TextFormattingRunProperties -c "calc.exe" > malicious.chx

Note: No public exploit code is available; this is a theoretical approach.

Blue Team (Defense)

Detection:

• Monitor for unusual CHX file downloads or email attachments.
• Use endpoint detection and response (EDR) to detect deserialization behavior (e.g., BinaryFormatter.Deserialize calls).
• Enable application whitelisting to prevent unknown executables.

Mitigation:

• Disable automatic file parsing in ShockLine if possible.
• Use network segmentation to limit exposure.
• Apply virtual patching via WAF or IPS if the software has a web interface.

Indicators of Compromise (IOCs)

• File Hashes: (None available; generate upon discovery)
• Network Indicators: Connections to attacker-controlled IPs after exploitation.
• Process Anomalies: ShockLine.exe spawning cmd.exe, powershell.exe, or other shells.
• Registry/File System: Creation of suspicious files in temp directories.
• YARA Rule: (See Detection Engineering)

Detection Engineering

YARA Rule

rule CVE_2025_15348_Anritsu_ShockLine_CHX_Deserialization {
    meta:
        description = "Detects malicious CHX files exploiting CVE-2025-15348"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-15348"
    strings:
        $binary_formatter = { 00 01 00 00 00 FF FF FF FF 01 00 00 00 00 00 00 00 }  // BinaryFormatter header
        $chx_magic = "CHX"  // CHX file magic bytes (example)
        $suspicious_type = "System.Diagnostics.Process"  // Common gadget chain
    condition:
        $chx_magic at 0 and ($binary_formatter or $suspicious_type)
}

Sigma Rule

title: Anritsu ShockLine CHX Deserialization Exploit
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects process creation anomalies from ShockLine.exe indicative of CVE-2025-15348 exploitation
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\ShockLine.exe'
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
            - '\wscript.exe'
            - '\cscript.exe'
    condition: selection
falsepositives:
    - Legitimate administrative use
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-15348 Anritsu ShockLine CHX Deserialization - Potential C2"; flow:to_server,established; content:"|00 01 00 00 00 FF FF FF FF|"; depth:8; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate: Disconnect Anritsu ShockLine systems from untrusted networks.
2. User Awareness: Train users not to open CHX files from untrusted sources.
3. Virtual Patching: If a web interface exists, deploy WAF rules to block CHX file uploads.

Long-Term:

• Contact Anritsu for an official patch or workaround.
• Consider replacing ShockLine with a patched alternative if available.
• Implement application control to block untrusted deserialization.

Workaround: If the software allows, disable CHX file parsing or use a sandbox to open such files.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Analyst