CVE-2025-7976

Executive Summary

CVE-2025-7976 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 is currently unpatched. No public proof-of-concept (PoC) or exploit code has been released, but the risk remains significant for organizations using ShockLine in test and measurement environments.

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: Local (requires user interaction)
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (victim must open a malicious file or page)
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

Threat Level: High. Although user interaction is required, the lack of a patch and the potential for lateral movement in test networks make this a serious concern.

Deep Dive & Mechanics

The vulnerability is a classic deserialization of untrusted data (CWE-502). Anritsu ShockLine uses CHX files to store configuration or measurement data. When the application deserializes these files, it does not validate the data stream, allowing an attacker to inject malicious serialized objects. Upon deserialization, these objects can execute arbitrary code within the ShockLine process.

Key technical details:

• Attack Vector: The attacker delivers a malicious CHX file via email, download, or a compromised website.
• Trigger: The victim opens the file in ShockLine, triggering the deserialization routine.
• Impact: Full control over the ShockLine application, potentially leading to data theft, system compromise, or lateral movement within the test network.

Vulnerable vs. Patched Code

Since no patch is available, a direct code comparison is not possible. However, the vulnerability likely stems from the use of insecure deserialization functions (e.g., BinaryFormatter in .NET or pickle in Python) without type validation or allowlists.

Vulnerable pattern (pseudocode):

// Vulnerable: No validation before deserialization
object obj = new BinaryFormatter().Deserialize(stream);

Patched pattern (hypothetical):

// Patched: Validate type before deserialization
var formatter = new BinaryFormatter();
formatter.Binder = new SafeBinder(); // Restrict allowed types
object obj = formatter.Deserialize(stream);

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Anritsu ShockLine installed on a target machine.
• Ability to deliver a malicious CHX file (e.g., via phishing email).

Steps:

1. Craft a malicious serialized payload using a tool like ysoserial.net (for .NET) or pickle (for Python).
2. Embed the payload into a CHX file structure.
3. Deliver the file to the victim.
4. When the victim opens the file in ShockLine, the payload executes.

Example payload generation (ysoserial.net):

ysoserial.exe -f BinaryFormatter -g TextFormattingRunProperties -c "calc.exe" > exploit.chx

Note: No public exploit code is available; this is a conceptual example.

Blue Team (Detection & Defense)

Defensive measures:

• Restrict execution of ShockLine to least privilege accounts.
• Use application whitelisting to block untrusted CHX files.
• Monitor for anomalous child processes spawned by ShockLine.
• Deploy endpoint detection and response (EDR) rules for deserialization attacks.

Indicators of Compromise (IOCs)

• File Hashes: (None available; monitor for suspicious CHX files)
• Network Indicators: Connections to known malicious IPs or domains from the ShockLine process.
• Process Indicators: Unexpected child processes (e.g., cmd.exe, powershell.exe) spawned by ShockLine.exe.
• Registry/File System: Unusual files written to %TEMP% or %APPDATA% by ShockLine.

Detection Engineering

YARA Rule

rule CVE_2025_7976_Deserialization {
    meta:
        description = "Detects malicious CHX files exploiting CVE-2025-7976"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-7976"
    strings:
        $magic = { 00 01 00 00 00 FF FF FF FF }  // Example .NET serialization header
        $payload = /(System\.Diagnostics\.Process|System\.Management\.Automation)/ nocase
    condition:
        $magic at 0 and $payload
}

Sigma Rule

title: CVE-2025-7976 - Anritsu ShockLine Deserialization RCE
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects suspicious child processes spawned by ShockLine.exe
author: Valters IT
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 tasks
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-7976 - Anritsu ShockLine CHX Deserialization RCE"; flow:to_server,established; content:"CHX"; nocase; content:"|00 01 00 00 00 FF FF FF FF|"; distance:0; within:8; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate actions:

1. Isolate ShockLine systems from untrusted networks.
2. Restrict user permissions to prevent opening untrusted CHX files.
3. Monitor for suspicious activity using the provided detection rules.

Long-term fixes:

• Await an official patch from Anritsu.
• Implement input validation and allowlist-based deserialization.
• Consider using a sandbox or virtualized environment for ShockLine.

Workarounds:

• Disable CHX file association or use file type blocking via Group Policy.
• Train users to avoid opening CHX files from untrusted sources.

Valters IT