How to remediate – UoW imapd AUTHENTICATE Command Remote Overflow

1. Introduction

The UoW imapd AUTHENTICATE Command Remote Overflow vulnerability allows an attacker to execute code on a remote IMAP server. This is due to insufficient input validation when handling long authentication commands, potentially leading to a buffer overflow and arbitrary code execution. Affected systems are typically email servers running the University of Washington’s (UoW) imapd service. Successful exploitation could compromise confidentiality, integrity, and availability of the server and associated data.

2. Technical Explanation

The vulnerability occurs because the UoW imapd service does not properly limit the length of the AUTHENTICATE command sent by a client. An attacker can send an excessively long string as part of this command, causing a buffer overflow on the server. This overflow may allow them to overwrite memory and execute arbitrary code. The CVE assigned to this vulnerability is CVE-1999-0005.

• Root cause: Lack of input validation on the length of the AUTHENTICATE command received by the imapd service.
• Exploit mechanism: An attacker connects to the IMAP server and sends a crafted AUTHENTICATE command with an overly long string, exceeding the buffer size allocated for handling the command. This can overwrite adjacent memory regions, potentially allowing code execution. For example, sending “A” repeated many times as part of the AUTHENTICATE command could trigger the overflow.
• Scope: Affected platforms are those running UoW imapd versions prior to any patch addressing this issue. Specific version ranges were not provided in available documentation.

3. Detection and Assessment

Confirming vulnerability requires checking the imapd service version and configuration. A thorough assessment involves attempting to trigger the overflow with a crafted command.

• Quick checks: Check the running imapd process using ps -ef | grep imapd. This will show the process ID and potentially reveal the version number if it’s included in the command line arguments.
• Scanning: Nessus plugin ID 16079 may detect this vulnerability, but results should be verified manually.

ps -ef | grep imapd

4. Solution / Remediation Steps

The primary solution is to contact your IMAP server vendor for a patch or updated version of the UoW imapd service that addresses this vulnerability.

4.1 Preparation

• Ensure you have access to a reliable method for restoring the previous configuration in case of issues. A roll back plan should include restoring the backed-up config and restarting the service.
• A change window may be required depending on your environment. Approval from relevant IT stakeholders is recommended.

4.2 Implementation

1. Step 1: Download and install the latest patch or updated version of UoW imapd from your vendor.
2. Step 2: Restart the imapd service to apply the changes.

4.3 Config or Code Example

Before

/* No specific configuration example available, as this is a code-level vulnerability requiring a patch from the vendor */

After

/* After applying the vendor's patch, the imapd service should have updated input validation logic. No direct config change expected. */

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this type of vulnerability.

• Practice 1: Least privilege – Run the imapd service with minimal necessary permissions to reduce the impact if exploited.
• Practice 2: Input validation – Implement strict input validation on all data received by the server, including the AUTHENTICATE command, to prevent excessively long strings or malicious characters.

4.5 Automation (Optional)

No automation script is provided as this vulnerability requires a vendor patch.

5. Verification / Validation

Confirming the fix involves checking the imapd version and attempting to re-trigger the overflow with a crafted command.

• Post-fix check: Verify the updated imapd version using ps -ef | grep imapd. The output should show the new version number.
• Re-test: Attempt to send a long AUTHENTICATE command (e.g., “A” repeated many times) and confirm that the server does not crash or exhibit unexpected behavior.
• Smoke test: Verify basic IMAP functionality, such as connecting to the server, logging in with valid credentials, and retrieving email messages.

ps -ef | grep imapd

6. Preventive Measures and Monitoring

Update security baselines and implement checks in CI/CD pipelines to prevent similar vulnerabilities.

• Baselines: Update your server security baseline to include the latest patch for UoW imapd or a secure alternative IMAP service.
• Pipelines: Add static application security testing (SAST) tools to your CI pipeline to scan code for potential buffer overflows and input validation issues.
• Asset and patch process: Implement a regular patch review cycle, prioritizing critical vulnerabilities like this one.

7. Risks, Side Effects, and Roll Back

Patching may cause temporary service disruption or compatibility issues.

• Risk or side effect 1: Patching could temporarily interrupt email services. Schedule patching during off-peak hours to minimize impact.
• Roll back: Restore the backed-up imapd configuration files and restart the service to revert to the previous version.

8. References and Resources

Links to relevant resources for this vulnerability.

• Vendor advisory or bulletin: No specific vendor advisory was found. Contact your IMAP server provider directly.
• NVD or CVE entry: CVE-1999-0005
• Product or platform documentation relevant to the fix: No specific documentation was found for this vulnerability beyond vendor guidance.