1. Introduction
Liferay Portal Remote Code Execution is a critical vulnerability affecting web applications running on Liferay servers. This allows an attacker to execute arbitrary commands on the server, potentially gaining full control. Systems running vulnerable versions of Liferay Portal are at risk. Successful exploitation could lead to complete compromise of confidentiality, integrity and availability.
2. Technical Explanation
The vulnerability (CVE-2020-7961) is due to the deserialization of untrusted data in Liferay Portal versions prior to 7.2.1 CE GA2. An unauthenticated attacker can send a crafted request that bypasses authentication and allows them to execute commands on the server.
- Root cause: Deserialization of untrusted data without proper validation allows attackers to inject malicious code.
- Exploit mechanism: An attacker sends a specially crafted HTTP request containing serialized Java objects to trigger remote code execution.
- Scope: Liferay Portal versions prior to 7.2.1 CE GA2 are affected.
3. Detection and Assessment
You can confirm if your system is vulnerable by checking the installed Liferay version, or using a vulnerability scanner.
- Quick checks: Check the Liferay Portal version via the web interface (usually in the “About” section).
- Scanning: Nessus signature ID 139580 can detect this vulnerability. This is an example only, other scanners may also provide detection.
- Logs and evidence: Look for suspicious activity related to deserialization errors or unexpected Java object creation in Liferay Portal logs (typically located in the server’s log directory).
# Example command placeholder:
# No direct command available, check version via web UI.
4. Solution / Remediation Steps
Apply the vendor-provided patch or upgrade to a secure version of Liferay Portal.
4.1 Preparation
- Ensure you have access to the vendor advisory and download the appropriate patch for your environment. A roll back plan is to restore from backup if patching fails.
- A change window may be required, depending on your organization’s policies. Approval from a system owner may also be needed.
4.2 Implementation
- Step 1: Download the latest Liferay Portal patch or upgrade package from the vendor’s website.
- Step 2: Stop all Liferay services.
- Step 3: Apply the patch or upgrade following the vendor’s instructions.
- Step 4: Start all Liferay services.
4.3 Config or Code Example
Before
# No specific configuration example available, as this is a code-level vulnerability requiring patching/upgrade. Affected versions are vulnerable by default.
After
# After applying the patch or upgrade to version 7.2.1 CE GA2 or later, the vulnerability should be mitigated.
4.4 Security Practices Relevant to This Vulnerability
Several security practices can help prevent this type of issue.
- Practice 1: Least privilege – limit the permissions granted to Liferay Portal processes and users to reduce the impact if exploited.
- Practice 2: Input validation – implement strict input validation on all user-supplied data to block malicious payloads.
4.5 Automation (Optional)
# No automation script available due to complexity of patching/upgrading Liferay Portal.
5. Verification / Validation
- Post-fix check: Verify the Liferay Portal version is 7.2.1 CE GA2 or later via the web interface.
- Re-test: Re-run the Nessus scan (ID 139580) to confirm the vulnerability is no longer detected.
- Smoke test: Verify basic Liferay Portal functionality, such as user login and content access, still works correctly.
- Monitoring: Monitor Liferay logs for deserialization errors or unexpected Java object creation patterns as an early warning sign of potential exploitation attempts.
# Post-fix command and expected output:
# Check version via web UI - Expected Output: "Liferay Portal 7.2.1 CE GA2" (or later)
6. Preventive Measures and Monitoring
Update security baselines, implement input validation checks in CI/CD pipelines, and maintain a regular patch cycle.
- Baselines: Update your Liferay Portal security baseline to require version 7.2.1 CE GA2 or later.
- Pipelines: Add static analysis (SAST) tools to your CI/CD pipeline to detect potential deserialization vulnerabilities in custom code.
- Asset and patch process: Implement a regular patch review cycle for Liferay Portal, aiming for timely application of security updates.
7. Risks, Side Effects, and Roll Back
Patching or upgrading can introduce compatibility issues with existing customizations. Restore from backup if problems occur.
- Risk or side effect 2: Service downtime during patching/upgrade process. Mitigation: Schedule maintenance window and communicate to users.
- Roll back: 1) Stop Liferay services. 2) Restore the database from backup. 3) Revert any configuration changes made during the upgrade. 4) Start Liferay services.
8. References and Resources
- Vendor advisory or bulletin: https://portal.liferay.dev/learn/security/vulnerability-response/CVE-2020-7961
- NVD or CVE entry: https://nvd.nist.gov/vuln/detail/CVE-2020-7961
- Product or platform documentation relevant to the fix: https://portal.liferay.dev/learn/security/vulnerability-response/CVE-2020-7961#upgrade-instructions