CVE-2025-27088

Remediation/Mitigation Strategy for CVE-2025-27088: Reflected Cross-Site Scripting (XSS) in oxyno-zeta/s3-proxy

This document outlines the remediation and mitigation strategy for the Reflected Cross-Site Scripting (XSS) vulnerability identified as CVE-2025-27088 in the oxyno-zeta/s3-proxy application.

1. Vulnerability Description

  • Vulnerability: Reflected Cross-Site Scripting (XSS)
  • Affected Software: oxyno-zeta/s3-proxy
  • Affected Versions: Versions prior to 4.18.1
  • Description: The application is vulnerable to reflected XSS. The folder-list template renders the Request.URL.Path variable directly into the HTML without proper sanitization or escaping. This allows an attacker to craft a malicious URL containing injected HTML or JavaScript. When a user visits the crafted URL, the malicious script is executed in the user’s browser, potentially allowing for session hijacking or phishing attacks.

2. Severity

  • CVSS Score: 8.4 (High)
  • Severity Level: High
  • Justification: The vulnerability allows for arbitrary script execution in the user’s browser. This can lead to:
    • Session Hijacking: Stealing a user’s session cookies, granting the attacker access to the application as that user.
    • Phishing: Redirecting users to fake login pages to steal their credentials.
    • Defacement: Altering the appearance of the web page.
    • Data Theft: Accessing and exfiltrating sensitive data displayed on the page.
  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: Required (User must click on a malicious link)
  • Scope: Changed (Exploit can affect other resources beyond the vulnerable component).
  • Confidentiality Impact: High
  • Integrity Impact: High
  • Availability Impact: None

3. Known Exploit

  • Exploitability: Attackers can craft malicious URLs that, when visited by a user, will execute arbitrary JavaScript code in their browser. This code can perform actions on behalf of the user, including stealing cookies or redirecting them to malicious websites.
  • Exploit Example (Conceptual): https://your-s3-proxy.example.com/<script>alert('XSS Vulnerability');</script> In this example, if the your-s3-proxy.example.com instance uses a vulnerable version of oxyno-zeta/s3-proxy, the JavaScript code <script>alert('XSS Vulnerability');</script> will be executed when the user visits the URL.

4. Remediation Strategy

The primary remediation strategy is to upgrade to a patched version of oxyno-zeta/s3-proxy.

  • Action: Upgrade to oxyno-zeta/s3-proxy version 4.18.1 or later.
  • Steps:
    1. Identify Affected Instances: Identify all installations of oxyno-zeta/s3-proxy within your environment.
    2. Backup: Before upgrading, create a backup of your existing oxyno-zeta/s3-proxy configuration and data. This will allow for easy rollback if any issues arise during the upgrade process.
    3. Upgrade: Follow the official upgrade instructions provided by the oxyno-zeta/s3-proxy project. This usually involves:
      • Stopping the running oxyno-zeta/s3-proxy instance.
      • Downloading the latest version of the software.
      • Replacing the existing installation with the new version.
      • Updating any required configuration files.
      • Starting the oxyno-zeta/s3-proxy instance.
    4. Verification: After upgrading, thoroughly test the application to ensure that it is functioning correctly and that the XSS vulnerability has been resolved. Specifically, try injecting JavaScript code into the URL to confirm that it is properly sanitized or escaped.
    5. Monitoring: Implement monitoring to detect any attempts to exploit the vulnerability. Look for suspicious characters (e.g., <script>, onerror, javascript:) in the URL path.

5. Mitigation Strategy (If immediate upgrade is not possible)

While upgrading is the preferred solution, the following mitigation strategies can be implemented as temporary measures to reduce the risk if an immediate upgrade is not feasible. These are not replacements for patching and should be treated as temporary measures only.

  • Input Validation and Sanitization:
    • Implement strict input validation on the server-side to filter out potentially malicious characters and patterns from the Request.URL.Path variable.
    • Sanitize the Request.URL.Path variable before rendering it in the HTML template. This can be done by escaping HTML entities (e.g., converting < to &lt;, > to &gt;, " to &quot;).
    • Note: Implementing input validation and sanitization requires careful consideration to avoid breaking legitimate functionality. Thorough testing is essential.
  • Content Security Policy (CSP):
    • Configure a Content Security Policy (CSP) to restrict the sources from which the browser is allowed to load resources. This can help prevent the execution of injected JavaScript code.
    • Example CSP: Content-Security-Policy: default-src ‘self’; script-src ‘self’; object-src ’none’; This CSP allows only scripts from the same origin to be executed.
    • Note: CSP can be complex to configure correctly and may require adjustments based on the specific requirements of your application. Start with a restrictive policy and gradually relax it as needed. Monitor for CSP violations.
  • Web Application Firewall (WAF):
    • Deploy a Web Application Firewall (WAF) to detect and block malicious requests targeting the XSS vulnerability.
    • Configure the WAF with rules to identify and block requests containing suspicious patterns in the URL path.
    • Note: A WAF can provide an additional layer of protection, but it is not a substitute for patching the underlying vulnerability. Regularly update the WAF rules to stay ahead of new attack techniques.
  • User Education:
    • Educate users about the risks of clicking on suspicious links. Train them to recognize phishing emails and other social engineering attacks.

6. Rollback Plan

If the upgrade or mitigation steps cause any unforeseen issues, the following rollback plan should be implemented:

  • Rollback the upgrade: Restore the backup created before the upgrade. This will revert the application to its previous state.
  • Disable the mitigation: Remove or disable any implemented mitigation measures (e.g., input validation, CSP, WAF rules).

7. Communication Plan

  • Communicate the vulnerability and the remediation/mitigation strategy to all relevant stakeholders, including developers, system administrators, and security personnel.
  • Provide regular updates on the progress of the remediation effort.
  • Notify users of the vulnerability and the steps they can take to protect themselves (e.g., being cautious about clicking on suspicious links).

8. Timeline

  • Identify Affected Instances: Immediately
  • Implement Mitigation (if necessary): Within 24 hours of identifying the vulnerability.
  • Upgrade to Version 4.18.1 or later: Within 72 hours of identifying the vulnerability.
  • Verification and Testing: Continuous.

This document will be updated as needed.

Assigner

Date

  • Published Date: 2025-02-20 22:33:51
  • Updated Date: 2025-02-21 22:15:14

More Details

CVE-2025-27088