Google Cloud Armor WAF rule to help mitigate CVE-2021-44228 Apache Log4j vulnerabilityGoogle Cloud Armor WAF rule to help mitigate CVE-2021-44228 Apache Log4j vulnerabilityProduct Manager, Cloud ArmorNetwork Specialist Manager

Editor’s note: As of 12/11/2021 at 5:30pm PST, this post was updated to include more information about the new Cloud Armor WAF rules and an explanation of the log snippet screenshot.

NIST has announced a recent vulnerability (CVE-2021-44228) in the Apache Log4j library. To help mitigate the effects of this vulnerability, Google Cloud Armor customers can now deploy a new preconfigured WAF rule that will help detect and, optionally, block attempted exploits of CVE-2021-44228. 


The Apache Log4j utility is a commonly used component for logging requests. On December 9, 2021, a vulnerability was reported that could allow a system running Apache Log4j version 2.14.1 or below to be compromised and allow an attacker to execute arbitrary code. 

On December 10, 2021, NIST published a critical Common Vulnerabilities and Exposure alert, CVE-2021-44228. More specifically, JNDI features used in configuration, log messages, and parameters do not protect against attacker controlled LDAP and other JNDI related endpoints. An attacker who can control log messages or log message parameters can execute arbitrary code loaded from remote servers when message lookup substitution is enabled.

If you have workloads you believe may be vulnerable, review Google Cloud’s mitigation steps below. You can determine your exposure by reading further details on the NIST website here

Addressing Apache Log4j vulnerability with Cloud Armor

Google Cloud’s Cloud Armor provides Denial of Service and Web Application Firewall (WAF) protection for applications and services hosted on Google Cloud, on your premises, or hosted elsewhere. The Cloud Armor team has worked closely with the Google Cybersecurity Action Team team to analyze this issue and prepare a response.  

In an attempt to help our customers address the Log4j vulnerability, we have introduced a new preconfigured WAF rule called “cve-canary” which can help detect and block exploit attempts of CVE-2021-44228. Cloud Armor customers can deploy the new rule into a new or existing Cloud Armor security policy following the below instructions. 

In order to detect or help mitigate exploit attempts of this CVE, you will need to create a new rule in your Cloud Armor security policy leveraging the preconfigured WAF rules called “cve-canary”. The rule can be created and inserted into a new or existing Cloud Armor security policy via the Google Cloud Console or the gCloud CLI.

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