How Cloudflare security responded to Log4j 2 vulnerability

On December 9, 2021, a serious vulnerability in the popular Java-based logging package Log4j was publicly disclosed. Cloudflare's security teams quickly responded by addressing two distinct questions: ensuring customer infrastructure protection and securing their own environment. The vulnerability allows an attacker to execute code on a remote server, making it one of the most serious vulnerabilities since Heartbleed and ShellShock. Upgrading to Log4j version 2.15 is recommended as a mitigation strategy. Cloudflare's response involved creating a timeline of events, addressing internal impact by identifying all software running on the JVM, reviewing external reports, and validating whether any assets were compromised through network analytics and endpoint analysis. They found no evidence of compromise and confirmed that their defense-in-depth approach worked effectively.