CVE-2025-27142

Remediation/Mitigation Strategy for CVE-2025-27142 - LocalSend Arbitrary File Write Vulnerability

This document outlines the remediation and mitigation strategy for CVE-2025-27142, a critical arbitrary file write vulnerability affecting versions of the LocalSend application prior to 1.17.0.

1. Vulnerability Description:

  • Vulnerability Name: LocalSend Arbitrary File Write
  • CVE ID: CVE-2025-27142
  • Description: The POST /api/localsend/v2/prepare-upload and POST /api/localsend/v2/upload endpoints in LocalSend versions prior to 1.17.0 lack proper path sanitization. This allows a malicious actor to craft a file transfer request that writes files to arbitrary locations on the system.
  • Attack Vector: A nearby device running a malicious LocalSend instance can send a crafted file transfer request.

2. Severity Assessment:

  • CVSS Score: 8.8 (High)
  • CVSS Vector: Based on the information, we can infer the general CVSS vector properties. Given the arbitrary file write leading to potential remote command execution, the CVSS vector would likely resemble something like: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.
    • AV:N (Network): The attack can originate from the local network.
    • AC:L (Low): Little effort is required to perform the attack.
    • PR:N (None): No privileges are required.
    • UI:R (Required): User interaction is required, particularly if the “Quick Save” feature is disabled. If “Quick Save” is enabled, the attack requires no user interaction.
    • S:U (Unchanged): The vulnerability only affects the vulnerable component.
    • C:H (High): High impact on confidentiality.
    • I:H (High): High impact on integrity.
    • A:H (High): High impact on availability.
  • Severity: Critical. This vulnerability allows for potential Remote Code Execution (RCE) which can lead to complete system compromise.

3. Known Exploit and Impact:

  • Exploit: A malicious actor on the local network can craft a file transfer request with a manipulated file path. This allows them to write files to sensitive locations on the target system.
  • Impact:
    • Remote Code Execution (RCE): Writing files to specific locations, such as startup folders on Windows or Bash configuration files on Linux, can allow the attacker to execute arbitrary commands.
    • System Compromise: Successful RCE allows the attacker to gain control of the affected system, potentially leading to data theft, malware installation, and denial of service.
    • Unintentional Data Loss/Modification: Though less likely given the RCE possibility, the arbitrary file write could overwrite or corrupt important system files.
  • Quick Save Feature Amplification: If the user has the “Quick Save” feature enabled, the vulnerability can be exploited silently without any user interaction, making the attack significantly easier to execute.

4. Remediation and Mitigation Strategy:

The primary remediation strategy is to update to the patched version of LocalSend. The following steps outline the complete strategy:

  • Immediate Action: Update to LocalSend Version 1.17.0 or Later

    • Critical: This is the most important step. Upgrade LocalSend to version 1.17.0 or a later version. This version contains the fix for the path sanitization issue.
    • Verification: Verify the installed version of LocalSend after the update to ensure the upgrade was successful.

  • Mitigation Measures (If Update is Not Immediately Possible):

    • Disable “Quick Save” Feature: If an immediate update is not possible, disable the “Quick Save” feature in LocalSend settings. This requires user interaction to accept file transfers, which provides an opportunity to review the file path and filename before accepting.
    • Network Segmentation: If feasible, isolate LocalSend users to a separate network segment to limit the potential attack surface. This may not be practical for all deployments.
    • Network Monitoring: Implement network monitoring to detect suspicious file transfer activity. Look for transfers to unusual directories or transfers with unusual file names.
    • Firewall Rules (Advanced): If possible, implement firewall rules to restrict access to the LocalSend API endpoints (/api/localsend/v2/prepare-upload and /api/localsend/v2/upload) to only trusted devices. This is complex and may break functionality if not implemented correctly.

  • Long-Term Security Practices:

    • Stay Informed: Subscribe to security advisories from LocalSend and other relevant software vendors to stay informed about potential vulnerabilities.
    • Regular Updates: Establish a process for regularly updating software to the latest versions, including security patches.
    • Security Awareness Training: Educate users about the risks of accepting files from untrusted sources, even on local networks.
    • Principle of Least Privilege: Ensure user accounts have only the necessary privileges to perform their tasks.

5. Communication:

  • Communicate the vulnerability and the required actions to all LocalSend users within the organization. Clearly explain the risks and the importance of updating to the latest version.

6. Testing and Validation:

  • After applying the update, test the LocalSend functionality to ensure that it is working as expected.
  • If possible, conduct penetration testing to verify that the vulnerability has been successfully mitigated.

7. Reporting:

  • Report the successful remediation to the appropriate stakeholders within the organization.

Assigner

Date

  • Published Date: 2025-02-25 20:15:38
  • Updated Date: 2025-02-28 13:35:22

More Details

CVE-2025-27142