How to remediate – UoW imap Server (uw-imapd) Arbitrary Remote File Access

1. Introduction

The UoW imap Server (uw-imapd) Arbitrary Remote File Access vulnerability allows an authenticated user to retrieve and manipulate files accessible via a shell. This could allow unauthorised access to sensitive information on the server. Systems running the affected IMAP daemon are at risk, particularly those where users have more permissions than necessary. A successful exploit may lead to confidentiality, integrity, or availability compromise of files accessible by the compromised account.

2. Technical Explanation

The vulnerability stems from insufficient restrictions on file access within the IMAP daemon. An authenticated user can request files beyond their intended scope if shell access is permitted. CVE-2002-1782 describes this issue. For example, an attacker with valid IMAP credentials could read configuration files containing passwords or other secrets if those files are accessible through the server’s file system.

• Root cause: The uw-imapd daemon does not adequately restrict which files authenticated users can access via shell commands.
• Exploit mechanism: An attacker logs in to the IMAP server with valid credentials and uses a command within the IMAP session to request access to restricted files.
• Scope: Affected platforms are those running the uw-imapd IMAP daemon, specifically versions prior to any fix addressing CVE-2002-1782.

3. Detection and Assessment

Confirming vulnerability requires checking the version of the installed IMAP daemon and assessing user permissions. A quick check can identify potentially vulnerable systems.

• Quick checks: Use the following command to determine the uw-imapd version: uw-imapd -v
• Scanning: Nessus plugin ID 30897 may detect this vulnerability, but results should be verified.
• Logs and evidence: Examine IMAP server logs for unusual file access attempts or shell command executions by authenticated users. Look for patterns indicating requests for files outside the expected user directories.

uw-imapd -v

4. Solution / Remediation Steps

The primary solution is to contact your vendor for a fix. The following steps outline preparation, implementation and verification.

4.1 Preparation

• Ensure you have access to the latest uw-imapd version from your vendor. A roll back plan involves restoring the pre-change backup of the configuration files and restarting the service.
• Change windows may be required depending on service impact. Approval should come from the IT Security team.

4.2 Implementation

1. Step 1: Download the latest version of uw-imapd from your vendor’s website.
2. Step 2: Stop the IMAP service using the appropriate system command (e.g., systemctl stop imap).
3. Step 3: Replace the existing uw-imapd executable with the new version.
4. Step 4: Restart the IMAP service using the appropriate system command (e.g., systemctl start imap).

4.3 Config or Code Example

Before

# No specific file access restrictions in uw-imapd configuration

After

# Vendor provided updated configuration with stricter file access controls.  Consult vendor documentation for details.

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this type of issue.

• Practice 1: Least privilege ensures users only have the minimum permissions required, limiting damage from a compromised account.
• Practice 2: Input validation prevents attackers from injecting malicious commands or requests to access restricted files.

4.5 Automation (Optional)

# Example Ansible playbook snippet - use with caution!
- name: Update uw-imapd package
  package:
    name: uw-imapd
    state: latest
  become: true # Requires elevated privileges

5. Verification / Validation

Confirm the fix by checking the updated version and re-attempting the earlier detection method. A service smoke test will ensure functionality remains.

• Post-fix check: Run uw-imapd -v to confirm the installed version is the patched version provided by your vendor.
• Re-test: Re-run the initial file access attempt (if possible in a safe environment) to verify it no longer succeeds.
• Smoke test: Verify users can still log in to IMAP and send/receive emails without issues.

uw-imapd -v

6. Preventive Measures and Monitoring

Update security baselines to include this patch, and consider adding checks in your CI/CD pipeline.

• Baselines: Update your server security baseline or policy to require the latest uw-imapd version with file access restrictions enabled.
• Pipelines: Add a static analysis check (SAST) to review uw-imapd configuration files for insecure settings during deployment.
• Asset and patch process: Implement a regular patch cycle for all servers, including IMAP servers, to ensure timely application of security updates.

7. Risks, Side Effects, and Roll Back

Updating uw-imapd may introduce compatibility issues with existing clients or configurations.

• Risk or side effect 2: Service interruption during the update process – schedule updates during off-peak hours.
• Roll back: Restore the pre-change backup of uw-imapd configuration files and restart the service. If necessary, revert to the previous version of the executable.

8. References and Resources

• Vendor advisory or bulletin: http://www.washington.edu/imap/IMAP-FAQs/index.html#5.1
• NVD or CVE entry: CVE-2002-1782
• Product or platform documentation relevant to the fix: Consult your uw-imapd vendor's documentation for specific configuration instructions.