CVE-2025-9870

Executive Summary

CVE-2025-9870 is a local privilege escalation vulnerability in Razer Synapse 3, specifically within the Philips HUE module installer. The flaw allows an attacker with low-privileged code execution on a target system to abuse a link-following weakness (CWE-59) to delete arbitrary files as SYSTEM. By creating a symbolic link, the attacker can redirect the installer’s file operations to delete critical system files, potentially leading to full system compromise. The vulnerability has a CVSS score of 7.8 (High) and currently has no known patch or public exploit. This report provides a comprehensive technical analysis, detection strategies, and mitigation recommendations.

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). The risk is limited to systems where Razer Synapse 3 is installed and an attacker has already gained low-privileged access.

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) – The attacker must have local access to the system.
• Attack Complexity: Low (AC:L) – No special conditions are required.
• Privileges Required: Low (PR:L) – The attacker needs low-privileged code execution.
• User Interaction: None (UI:N) – No user action is needed.
• Scope: Unchanged (S:U) – The vulnerability does not cross security boundaries.
• Confidentiality Impact: High (C:H) – Arbitrary file deletion can expose sensitive data.
• Integrity Impact: High (I:H) – System files can be deleted, leading to instability.
• Availability Impact: High (A:H) – Deletion of critical files can cause denial of service.

Threat Level: High. The vulnerability is easy to exploit once low-privileged access is obtained, and the impact is severe.

Deep Dive & Mechanics

The vulnerability resides in the Razer Synapse 3 Philips HUE module installer. The installer performs file operations (likely deletion of temporary files or uninstallation routines) without properly validating symbolic links. An attacker can create a symbolic link pointing to a critical system file (e.g., C:\Windows\System32\config\SAM or C:\Windows\System32\drivers\etc\hosts). When the installer runs with SYSTEM privileges, it follows the link and deletes the target file.

Attack Flow:

1. Attacker gains low-privileged code execution on the target system (e.g., via phishing, malware, or other means).
2. Attacker identifies the vulnerable installer path (e.g., C:\ProgramData\Razer\Synapse3\Service\...).
3. Attacker creates a symbolic link from a predictable file path used by the installer to a critical system file.
4. The installer runs (either automatically or triggered by the attacker) and deletes the linked file as SYSTEM.
5. The attacker can then exploit the resulting system instability or missing security controls to escalate privileges.

Key Weakness: The installer does not use NtCreateFile with FILE_OPEN_REPARSE_POINT flag or equivalent checks to prevent following symbolic links.

Vulnerable vs. Patched Code

No patched code is available. The vulnerable code is in the Philips HUE module installer (likely a DLL or executable). The fix would involve:

• Using CreateFile with FILE_FLAG_OPEN_REPARSE_POINT to prevent following symbolic links.
• Validating that the target file is within the expected directory.
• Running the installer with reduced privileges or impersonating a lower-privileged user.

Vulnerable Code (Conceptual):

// Vulnerable: Deletes file without checking for symbolic links
DeleteFileW(L"C:\\ProgramData\\Razer\\Temp\\philips_hue_uninstall.log");

Patched Code (Conceptual):

// Patched: Uses reparse point flag to avoid following links
HANDLE hFile = CreateFileW(L"C:\\ProgramData\\Razer\\Temp\\philips_hue_uninstall.log",
                           DELETE, 0, NULL, OPEN_EXISTING,
                           FILE_FLAG_OPEN_REPARSE_POINT, NULL);
if (hFile != INVALID_HANDLE_VALUE) {
    FILE_DISPOSITION_INFO info;
    info.DeleteFile = TRUE;
    SetFileInformationByHandle(hFile, FileDispositionInfo, &info, sizeof(info));
    CloseHandle(hFile);
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Low-privileged shell on a Windows system with Razer Synapse 3 installed.
• Ability to create symbolic links (requires SeCreateSymbolicLinkPrivilege, which is often granted to low-privileged users by default on some systems, or use of mklink if available).

Exploitation Steps:

1. Identify the vulnerable installer path. Example: C:\ProgramData\Razer\Synapse3\Service\Temp\philips_hue_uninstall.log
2. Create a symbolic link from that path to a critical system file:

   mklink C:\ProgramData\Razer\Synapse3\Service\Temp\philips_hue_uninstall.log C:\Windows\System32\config\SAM
   

3. Trigger the installer (e.g., by running the Philips HUE module uninstaller or waiting for a scheduled task).
4. The installer deletes the SAM file, causing the system to become unstable or allowing the attacker to boot into recovery mode and reset the administrator password.

Alternative Target: C:\Windows\System32\drivers\etc\hosts to disrupt network security.

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

Blue Team (Detection & Defense)

Detection:

• Monitor for creation of symbolic links by low-privileged processes to system-critical paths.
• Monitor for file deletion events on system-critical files (e.g., SAM, SYSTEM, SECURITY hives).
• Use Sysmon Event ID 1 (Process creation) to detect mklink usage.
• Use Sysmon Event ID 11 (FileCreate) to detect symbolic link creation.

Defense:

• Apply the principle of least privilege: Ensure users do not have SeCreateSymbolicLinkPrivilege.
• Use Windows Defender Exploit Guard to block symbolic link creation from untrusted processes.
• Disable or remove the Philips HUE module if not needed.
• Monitor for Razer Synapse 3 updates and apply patches when available.

Indicators of Compromise (IOCs)

File Paths:

• C:\ProgramData\Razer\Synapse3\Service\Temp\philips_hue_uninstall.log (legitimate path)
• C:\Windows\System32\config\SAM (target)
• C:\Windows\System32\config\SYSTEM (target)
• C:\Windows\System32\drivers\etc\hosts (target)

Processes:

• Razer Synapse 3 Installer (e.g., RazerSynapseInstaller.exe)
• cmd.exe or powershell.exe creating symbolic links

Registry Keys:

• HKLM\SOFTWARE\Razer\Synapse3\Service\PhilipsHue (module configuration)

Network:

• No network indicators; this is a local vulnerability.

Detection Engineering

YARA Rule

rule CVE_2025_9870_Symlink_Abuse {
    meta:
        description = "Detects symbolic link creation targeting system files for CVE-2025-9870"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-9870"
    strings:
        $mklink = "mklink" nocase
        $target1 = "\\config\\SAM" nocase
        $target2 = "\\config\\SYSTEM" nocase
        $target3 = "\\drivers\\etc\\hosts" nocase
        $razer_path = "Razer\\Synapse3" nocase
    condition:
        $mklink and ($target1 or $target2 or $target3) and $razer_path
}

Sigma Rule

title: CVE-2025-9870 - Razer Synapse 3 Symbolic Link Privilege Escalation
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects creation of symbolic links to system-critical files by Razer Synapse 3 processes
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-9870
logsource:
    product: windows
    service: sysmon
detection:
    selection:
        EventID: 11  # FileCreate
        TargetFilename|contains:
            - '\\config\\SAM'
            - '\\config\\SYSTEM'
            - '\\drivers\\etc\\hosts'
        Image|contains: 'Razer\\Synapse3'
    condition: selection
falsepositives:
    - Legitimate administrative tasks
level: high

Suricata Rule

alert ip any any -> any any (msg:"CVE-2025-9870 - Razer Synapse 3 Symlink Abuse"; content:"mklink"; content:"Razer"; content:"Synapse3"; content:"config"; content:"SAM"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Philips HUE module in Razer Synapse 3 if not required.
2. Restrict symbolic link creation by removing SeCreateSymbolicLinkPrivilege from low-privileged users.
3. Monitor for suspicious file deletions using Sysmon or EDR.

Long-term Fix:

• Apply a patch from Razer when available.
• Replace the vulnerable installer with a version that validates symbolic links.

Workaround:

• Use Windows Defender Application Control (WDAC) to block untrusted symbolic link creation.

Valters IT Signature: This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.