CVE-2025-0413

Executive Summary

CVE-2025-0413 is a high-severity local privilege escalation vulnerability in Parallels Desktop, specifically within the Technical Data Reporter component. The flaw allows an attacker with low-privileged code execution on the host system to escalate privileges to root by abusing a symbolic link (symlink) to change permissions on arbitrary files. This vulnerability has a CVSS score of 7.8, indicating significant impact on confidentiality, integrity, and availability. No public proof-of-concept (PoC) or patch details are currently available, but the vulnerability is confirmed by ZDI (ZDI-CAN-25014). The EPSS score is 0.0%, suggesting low exploitation likelihood in the wild at this time.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
• Base Score: 7.8 (High)
• Attack Vector: Local (AV:L) – Requires local access to the host system.
• Attack Complexity: Low (AC:L) – No special conditions needed.
• Privileges Required: Low (PR:L) – Attacker needs 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 permissions can be modified.
• Availability Impact: High (A:H) – Potential for denial of service or system instability.

Threat Level: High. Local privilege escalation to root can lead to full host compromise, data exfiltration, and persistence.

Deep Dive & Mechanics

The vulnerability resides in the Technical Data Reporter component of Parallels Desktop. This component is designed to collect and report technical data for debugging purposes. The flaw is a classic symlink following vulnerability (CWE-59: Improper Link Resolution Before File Access).

Mechanism:

1. The Technical Data Reporter service runs with elevated privileges (root).
2. It performs file operations (e.g., writing logs, creating temporary files) in a directory writable by low-privileged users.
3. An attacker with low-privileged code execution can create a symbolic link (symlink) pointing from a file the service expects to write to, to a critical system file (e.g., /etc/sudoers, /etc/passwd, or a binary).
4. When the service writes to or modifies the file, it follows the symlink and inadvertently changes the permissions of the target file.
5. The attacker can then leverage the modified permissions to escalate privileges to root.

Key Weakness: The service does not validate whether the file path is a symlink before performing privileged operations. This allows an attacker to redirect file operations to arbitrary locations.

Vulnerable vs. Patched Code

No specific code snippets are available for this CVE. However, the vulnerable pattern is:

Vulnerable (pseudocode):

// Service writes to a file without checking for symlinks
FILE *fp = fopen("/tmp/techdata.log", "w");
if (fp) {
    fprintf(fp, "Data...");
    fclose(fp);
    // No check if /tmp/techdata.log is a symlink
}

Patched (pseudocode):

// Service checks for symlinks before writing
struct stat st;
if (lstat("/tmp/techdata.log", &st) == 0) {
    if (S_ISLNK(st.st_mode)) {
        // Reject symlink or use safe directory
        return -1;
    }
}
FILE *fp = fopen("/tmp/techdata.log", "w");
if (fp) {
    fprintf(fp, "Data...");
    fclose(fp);
}

The patch would involve using lstat() to detect symlinks and either aborting the operation or using a secure directory (e.g., one owned by root with restricted permissions).

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• Local access to a host running Parallels Desktop (vulnerable version).
• Ability to execute low-privileged code (e.g., via a malicious script or user-level exploit).

Exploitation Steps:

1. Identify the target directory: The Technical Data Reporter writes to a predictable location (e.g., /tmp/parallels_techdata).
2. Create a symlink: Replace the expected file with a symlink to a critical system file.

   ln -sf /etc/sudoers /tmp/parallels_techdata/log.txt
   

3. Trigger the service: Force the Technical Data Reporter to run (e.g., via a GUI action or command).
4. Escalate privileges: After the service modifies the symlinked file, the target file (e.g., /etc/sudoers) will have altered permissions (e.g., world-writable).
5. Gain root access: Modify the target file to add a backdoor user or grant sudo privileges.

   echo "attacker ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers
   sudo -u root /bin/bash
   

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

Blue Team (Defense & Detection)

Detection:

• Monitor for symlink creation in directories used by Parallels Desktop (e.g., /tmp/parallels_*).
• Alert on file permission changes to critical system files (e.g., /etc/sudoers, /etc/passwd).
• Use file integrity monitoring (FIM) to detect unauthorized modifications.

Prevention:

• Apply the vendor patch when available.
• Restrict write access to /tmp and other world-writable directories for sensitive services.
• Use mandatory access controls (e.g., SELinux, AppArmor) to confine the Technical Data Reporter.
• Implement symlink protection (e.g., protected_symlinks sysctl setting).

Indicators of Compromise (IOCs)

• File System:
  • Unexpected symlinks in /tmp/parallels_* directories.
  • Modified permissions on /etc/sudoers, /etc/passwd, or /etc/shadow.
  • New user accounts or sudo entries.
• Process:
  • Unusual child processes spawned by the Technical Data Reporter.
  • Processes accessing critical system files unexpectedly.
• Network:
  • Outbound connections from the host to unknown IPs (if data exfiltration occurs).

Example IOC (Symlink):

ls -la /tmp/parallels_techdata/
lrwxrwxrwx 1 attacker attacker 12 Jan 1 00:00 log.txt -> /etc/sudoers

Detection Engineering

YARA Rule

rule CVE_2025_0413_Symlink_Abuse {
    meta:
        description = "Detects symlink creation targeting critical files in Parallels Desktop directories"
        author = "Valters IT"
        date = "2025-01-01"
        reference = "CVE-2025-0413"
    strings:
        $symlink_target = "/etc/sudoers" nocase
        $symlink_target2 = "/etc/passwd" nocase
        $symlink_target3 = "/etc/shadow" nocase
        $parallels_dir = "/tmp/parallels_" nocase
    condition:
        $parallels_dir and any of ($symlink_target*)
}

Sigma Rule

title: CVE-2025-0413 - Parallels Desktop Symlink Privilege Escalation
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects symlink creation in Parallels Desktop directories targeting critical system files
author: Valters IT
date: 2025-01-01
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-0413
logsource:
    category: file_event
    product: linux
detection:
    selection:
        TargetFilename|contains:
            - '/tmp/parallels_'
        TargetFilename|endswith:
            - '/etc/sudoers'
            - '/etc/passwd'
            - '/etc/shadow'
    condition: selection
falsepositives:
    - Legitimate administrative actions
level: high

Suricata Rule

alert file any any -> any any (msg:"CVE-2025-0413 - Parallels Desktop Symlink to Critical File"; file.name:"/etc/sudoers"; file.name:"/etc/passwd"; file.name:"/etc/shadow"; file.dir:"/tmp/parallels_"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected systems: If possible, disconnect hosts running Parallels Desktop from sensitive networks.
2. Restrict local access: Limit user accounts and enforce least privilege.
3. Monitor for exploitation: Deploy the detection rules above.

Long-term Fix:

• Apply the official patch from Parallels when released.
• Upgrade to a patched version of Parallels Desktop.

Workarounds:

• Remove write permissions for non-root users on directories used by Technical Data Reporter.
• Use a custom SELinux policy to prevent symlink following in /tmp/parallels_*.
• Disable the Technical Data Reporter service if not needed.

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