CVE-2025-9869

Executive Summary

CVE-2025-9869 is a local privilege escalation vulnerability in Razer Synapse 3, specifically within the Razer Synapse Service. The flaw allows an attacker with low-privileged code execution on the target system to create a symbolic link, abusing the service to delete arbitrary files. This can be leveraged to escalate privileges to SYSTEM and execute arbitrary code. The vulnerability has a CVSS score of 7.8 (High) and is currently unpatched. No public proof-of-concept or exploit code has been released, and the EPSS score is 0.0%, indicating low exploitation activity in the wild.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a local privilege escalation in a proprietary Windows application (Razer Synapse 3). No supply chain implications are present.

CVSS Breakdown & Threat Level

• CVSS Score: 7.8 (High)
• Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Local (AV:L) – requires local access to the system.
• Attack Complexity: Low (AC:L) – no special conditions needed.
• Privileges Required: Low (PR:L) – attacker must have low-privileged code execution.
• User Interaction: None (UI:N) – no user action required.
• Scope: Unchanged (S:U) – vulnerability does not cross trust boundaries.
• Confidentiality Impact: High (C:H) – full system compromise possible.
• Integrity Impact: High (I:H) – arbitrary file deletion and code execution.
• Availability Impact: High (A:H) – can lead to system instability or denial of service.

Threat Level: High. Although no public exploit exists, the vulnerability is easily exploitable once low-privileged access is obtained. The lack of a patch makes it a significant risk for systems running Razer Synapse 3.

Deep Dive & Mechanics

The vulnerability resides in the Razer Synapse Service, which runs with SYSTEM privileges. The service performs file operations without proper validation of symbolic links. An attacker with low-privileged code execution can create a symbolic link pointing to a critical system file (e.g., C:\Windows\System32\config\SAM). When the service attempts to delete a file in a directory it controls, it follows the symbolic link and deletes the target file instead.

Key Components:

• Razer Synapse Service: A Windows service running as SYSTEM.
• Symbolic Link (Symlink): A file system object that points to another file or directory.
• Arbitrary File Deletion: The service deletes files without checking if the path is a symlink.

Attack Flow:

1. Attacker gains low-privileged code execution on the target system.
2. Attacker identifies a directory writable by the low-privileged user that the Razer Synapse Service will delete files from.
3. Attacker creates a symbolic link in that directory pointing to a critical system file (e.g., C:\Windows\System32\config\SAM).
4. The Razer Synapse Service, running as SYSTEM, deletes the file, following the symlink.
5. Attacker leverages the deletion to cause a denial of service or, in combination with other techniques, escalate privileges to SYSTEM.

Root Cause: Improper handling of symbolic links (CWE-59: Improper Link Resolution Before File Access).

Vulnerable vs. Patched Code

No patched version is available. The vulnerable code is in the Razer Synapse Service binary. Below is a conceptual comparison:

Vulnerable Code (Pseudocode):

void DeleteFileInDirectory(const std::wstring& directory) {
    for (const auto& entry : std::filesystem::directory_iterator(directory)) {
        // No check for symbolic link
        std::filesystem::remove(entry.path());
    }
}

Patched Code (Hypothetical):

void DeleteFileInDirectory(const std::wstring& directory) {
    for (const auto& entry : std::filesystem::directory_iterator(directory)) {
        if (std::filesystem::is_symlink(entry.status())) {
            // Skip symbolic links
            continue;
        }
        std::filesystem::remove(entry.path());
    }
}

The patched version would check if the file is a symbolic link before deletion, preventing the attack.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Low-privileged shell on a Windows system with Razer Synapse 3 installed.
• Knowledge of a directory writable by the user that the service will delete files from (e.g., C:\ProgramData\Razer\Synapse3\Temp).

Exploit Steps:

1. Identify the target directory: C:\ProgramData\Razer\Synapse3\Temp
2. Create a symbolic link:

   mklink C:\ProgramData\Razer\Synapse3\Temp\evil_link C:\Windows\System32\config\SAM
   

3. Trigger the service to delete files in that directory (e.g., by performing an action in Razer Synapse 3 that cleans up temp files).
4. The service deletes C:\Windows\System32\config\SAM, causing system instability or allowing further privilege escalation.

Note: No public exploit code is available. This is a conceptual demonstration.

Blue Team (Detection & Prevention)

Detection:

• Monitor for creation of symbolic links in directories used by Razer Synapse Service.
• Alert on file deletion events targeting critical system files (e.g., SAM, SYSTEM, SECURITY).
• Use Sysmon Event ID 1 (Process Creation) to detect mklink usage.

Prevention:

• Apply the principle of least privilege to the Razer Synapse Service.
• Use Windows Defender Exploit Guard to block symbolic link creation from low-privileged processes.
• Restrict write access to directories used by the service.

Indicators of Compromise (IOCs)

• File Paths:
  • C:\ProgramData\Razer\Synapse3\Temp\* (suspicious symlinks)
  • C:\Windows\System32\config\SAM (deletion)
• Process Creation:
  • cmd.exe or powershell.exe executing mklink
• Event IDs:
  • Sysmon Event ID 1 (Process Creation) with mklink
  • Windows Security Event ID 4663 (File Deletion) for critical system files
• Registry: N/A
• Network: N/A

Detection Engineering

YARA Rule

rule CVE_2025_9869_Razer_Symlink_Abuse {
    meta:
        description = "Detects symbolic link creation targeting Razer Synapse directories"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-9869"
    strings:
        $mklink = "mklink" nocase
        $razer_path = "Razer\\Synapse3" nocase
    condition:
        $mklink and $razer_path
}

Sigma Rule

title: CVE-2025-9869 Razer Synapse Symlink Abuse
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects creation of symbolic links in Razer Synapse directories
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-9869
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\cmd.exe'
        CommandLine|contains: 'mklink'
        CommandLine|contains: 'Razer\Synapse3'
    condition: selection
falsepositives:
    - Legitimate Razer Synapse operations (rare)
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-9869 Razer Synapse Symlink Abuse"; flow:to_server; content:"mklink"; nocase; content:"Razer"; nocase; within:100; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Razer Synapse 3 if not essential for operations.
2. Restrict write access to directories used by the Razer Synapse Service (e.g., C:\ProgramData\Razer\Synapse3\Temp) to only SYSTEM and Administrators.
3. Monitor for symlink creation using the provided detection rules.

Long-Term Fix:

• Await an official patch from Razer. In the meantime, consider using alternative input device management software.
• Implement application whitelisting to prevent unauthorized executables from running.

Workaround:

• Use Windows Defender Exploit Guard to block symbolic link creation from low-integrity processes.

Valters IT