1. Introduction
The remote Gentoo host is missing security updates for SquirrelMail, specifically addressing a Remote Code Execution vulnerability (GLSA-201709-13). This allows a remote attacker to execute arbitrary shell commands by enticing a user to open a malicious email attachment. Systems running vulnerable versions of SquirrelMail are at risk. Impact: Confidentiality, integrity and availability may be compromised if exploited successfully.
2. Technical Explanation
The vulnerability in SquirrelMail (GLSA-201709-13) stems from mishandling the sendmail.cf file within a popen call. This allows an attacker to inject and execute arbitrary shell commands when a user opens a specially crafted email attachment. The vulnerability is tracked as CVE-2017-7692.
- Root cause: Incorrect handling of the
sendmail.cffile in the popen call leads to command injection. - Exploit mechanism: An attacker crafts a malicious email attachment that, when opened by a user, triggers the vulnerable code path and executes arbitrary shell commands on the server.
- Scope: SquirrelMail versions prior to the fix are affected.
3. Detection and Assessment
Confirming vulnerability requires checking the installed version of SquirrelMail. As Gentoo has discontinued support, identifying its presence is key.
- Quick checks: Use the following command to check if SquirrelMail is installed:
emerge -pv mail-client/squirrelmail. If it returns a listing, SquirrelMail is present. - Scanning: Nessus plugin ID 109678 may detect this vulnerability. This is an example only and should be verified.
emerge -pv mail-client/squirrelmail4. Solution / Remediation Steps
Gentoo has discontinued support for SquirrelMail, so removing it is the recommended solution.
4.1 Preparation
- Dependencies: None. Change window: Standard maintenance window recommended, with approval from IT management.
4.2 Implementation
- Step 1: Unmerge the SquirrelMail package using the following command:
emerge --unmerge 'mail-client/squirrelmail'.
4.3 Config or Code Example
There is no config or code change needed, as the solution involves removing the package.
4.4 Security Practices Relevant to This Vulnerability
Removing unsupported software significantly reduces risk. Regular patch management and vulnerability scanning are also essential practices.
- Practice 1: Discontinue use of end-of-life software to eliminate known vulnerabilities.
- Practice 2: Implement a regular patch cadence for all supported software to address security issues promptly.
4.5 Automation (Optional)
No automation is provided, as the recommended solution involves removing the package.
5. Verification / Validation
Verify the fix by confirming SquirrelMail has been removed from the system.
- Post-fix check: Run
emerge -pv mail-client/squirrelmail. The command should not return any results, indicating that the package is no longer installed. - Re-test: Attempt to locate any SquirrelMail files or directories on the system; none should be found.
- Monitoring: Monitor system logs for any errors related to missing dependencies that may have relied on SquirrelMail (example only).
emerge -pv mail-client/squirrelmail6. Preventive Measures and Monitoring
Regularly review installed software and remove unsupported packages. Implement a vulnerability scanning process to identify outdated or vulnerable applications.
- Baselines: Update security baselines to exclude end-of-life software like SquirrelMail.
- Pipelines: Integrate SCA (Software Composition Analysis) tools into CI/CD pipelines to detect vulnerable dependencies.
- Asset and patch process: Establish a regular review cycle for installed software, focusing on patching and removal of unsupported applications.
7. Risks, Side Effects, and Roll Back
- Roll back: Re-emerge the package using
emerge --unmerge 'mail-client/squirrelmail'(not recommended).
8. References and Resources
Official Gentoo security advisory for GLSA-201709-13 provides detailed information about this vulnerability.
- Vendor advisory or bulletin: https://security.gentoo.org/glsa/201709-13
- NVD or CVE entry: CVE-2017-7692