This repository provides CISA's guidance and an overview of related software regarding the Log4j vulnerability (CVE-2021-44228). CISA urges users and administrators to upgrade to Log4j 2.17.1 (Java 8), 2.12.4 (Java 7) and 2.3.2 (Java 6), and review and monitor the Apache Log4j Security Vulnerabilities webpage for updates and mitigation guidance.

The information in this repository is provided "as is" for informational purposes only and is being assembled and updated by CISA through collaboration with the broader cybersecurity community. Inquire with the manufacturer or their respective online resources for the most up-to-date information regarding any specific product listed. CISA does not endorse any commercial product or service, including any subjects of analysis. Any reference to specific commercial products, processes, or services by service mark, trademark, manufacturer, or otherwise, does not constitute or imply their endorsement, recommendation, or favoring by CISA.

• CISA Apache Log4j Vulnerability Guidance
• CISA ED 22-02: Apache Log4j Recommended Mitigation Measures
• CISA ALERT (AA21-356A): Mitigating Log4Shell and Other Log4j-Related Vulnerabilities
• Emergency Directive 22-02 Mitigate Apache Log4j Vulnerability
• Statement from CISA Director Easterly on “Log4j” Vulnerability.

• Mitigating Log4Shell and Other Log4j-Related Vulnerabilities
• CISA Issues ED 22-02 Directing Federal Agencies to Mitigate Apache Log4j Vulnerabilities
• Apache Releases Log4j Version 2.15.0 to Address Critical RCE Vulnerability Under Exploitation
• CISA Creates Webpage for Apache Log4j Vulnerability CVE-2021-44228

National Vulnerability Database (NVD) Information: CVE-2021-44228

When updates are available, agencies must update software using Log4j to the newest version, which is the most effective and manageable long-term option. Where updating is not possible, the following mitigating measures can be considered as a temporary solution and apply to the entire solution stack.

• Disable Log4j library. Disabling software using the Log4j library is an effective measure, favoring controlled downtime over adversary-caused issues. This option could cause operational impacts and limit visibility into other issues.
• Disable JNDI lookups or disable remote codebases. This option, while effective, may involve developer work and could impact functionality.
• Disconnect affected stacks. Solution stacks not connected to agency networks pose a dramatically lower risk from attack. Consider temporarily disconnecting the stack from agency networks.
• Isolate the system. Create a “vulnerable network” VLAN and segment the solution stack from the rest of the enterprise network.
• Deploy a properly configured Web Application Firewall (WAF) in front of the solution stack. Deploying a WAF is an important, but incomplete, solution. While threat actors will be able to bypass this mitigation, the reduction in alerting will allow an agency SOC to focus on a smaller set of alerts.
• Apply micropatch. There are several micropatches available. They are not a part of the official update but may limit agency risk.
• Report incidents promptly to CISA and/or the FBI here.

For more information regarding CISA recommended mitigation measures please visit here.

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Instructions for creating a pull request using the GitHub Web UI can be found in PULL-EXAMPLE.md.

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