How to remediate – AIX bellmail Advisory : bellmail_advisory2.asc (IV92238) (IV92…

1. Introduction

The AIX bellmail Advisory : bellmail_advisory2.asc (IV92238) (IV92…) vulnerability affects versions of bellmail installed on AIX systems. This is a privilege escalation issue where a local attacker can gain root access. This impacts the confidentiality, integrity and availability of affected systems.

2. Technical Explanation

The vulnerable version of bellmail allows a local attacker to escalate privileges to root. The vulnerability stems from insecure permissions or flawed logic within the bellmail application itself. A successful exploit requires local access to the AIX system. This is tracked as CVE-2017-1093.

• Root cause: Insecure file permissions allow unauthorized modification of critical bellmail files.
• Exploit mechanism: An attacker can modify a bellmail configuration file or executable to execute arbitrary commands with root privileges. For example, an attacker could overwrite the setuid bit on the bellmail binary.
• Scope: AIX systems running vulnerable versions of bellmail are affected.

3. Detection and Assessment

You can check if a system is vulnerable by verifying the installed version of bellmail. A thorough assessment involves examining file permissions and configurations.

• Quick checks: Use the following command to list the installed bellmail version: ls -l /opt/bellmail/bin/bellmail (path may vary).
• Scanning: Nessus plugin ID 95891 can detect this vulnerability. This is provided as an example only.
• Logs and evidence: Check system logs for unusual activity related to bellmail, such as unexpected file modifications or process executions.

ls -l /opt/bellmail/bin/bellmail

4. Solution / Remediation Steps

Apply the fix available from IBM AIX website to resolve this vulnerability. Follow these steps carefully.

4.1 Preparation

• A change window may be required depending on your organization’s policies. Approval from system owners might be needed.

4.2 Implementation

1. Step 1: Download the patch from https://aix.software.ibm.com/aix/efixes/security/bellmail_advisory2.asc.
2. Step 2: Install the patch using the smitty applypatch command or equivalent method for your AIX version.
3. Step 3: Reboot the system to activate the patch.

4.3 Config or Code Example

Before

#Example - insecure permissions (actual permissions will vary)
-rwxr-xr-x   1 root system  123456 Jul 01 00:00 /opt/bellmail/bin/bellmail

After

#Example - secure permissions after patch (actual permissions will vary)
-rwxr-xr--   1 root system  123456 Jul 01 00:00 /opt/bellmail/bin/bellmail

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this type of vulnerability. Least privilege reduces the impact if exploited, and regular patch cadence ensures timely updates.

• Practice 1: Implement least privilege principles to limit user access rights.
• Practice 2: Establish a regular patch management process to apply security updates promptly.

4.5 Automation (Optional)

# Example Ansible playbook snippet (requires adaptation for your environment)
- name: Apply bellmail patch
  command: smitty applypatch -file /path/to/bellmail_advisory2.asc
  become: yes
  changed_when: true

5. Verification / Validation

Confirm the fix by verifying the installed version and re-running the initial detection method. A smoke test should confirm basic functionality remains intact.

• Post-fix check: Run ls -l /opt/bellmail/bin/bellmail and verify that the file permissions are secure (e.g., not world writable).
• Re-test: Re-run the command from section 3 to confirm the vulnerability is no longer detected.
• Smoke test: Verify that users can still send and receive emails using bellmail.
• Monitoring: Monitor system logs for any unusual activity related to bellmail, such as unexpected file modifications or process executions.

ls -l /opt/bellmail/bin/bellmail

6. Preventive Measures and Monitoring

Update security baselines and implement checks in CI pipelines to prevent similar vulnerabilities. A sensible patch review cycle is also important.

• Baselines: Update your AIX security baseline to include the latest bellmail patch requirements.
• Pipelines: Add a check to your CI pipeline to scan for known vulnerabilities in installed packages, including bellmail.
• Asset and patch process: Implement a monthly patch review cycle to ensure timely application of security updates.

7. Risks, Side Effects, and Roll Back

Applying the patch may cause temporary service interruption during reboot. If issues occur, restore from backup.

• Risk or side effect 1: Temporary service disruption during system reboot.
• Risk or side effect 2: Potential compatibility issues with other applications (unlikely but possible).
• Roll back: 1. Restore the system from a pre-patch backup or snapshot. 2. Verify that bellmail is running and functioning correctly.

8. References and Resources

• Vendor advisory or bulletin: https://aix.software.ibm.com/aix/efixes/security/bellmail_advisory2.asc
• NVD or CVE entry: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-1093
• Product or platform documentation relevant to the fix: IBM AIX documentation on applying patches.