CVE-2021-44228, also known as Log4Shell, is a critical security flaw discovered in Apache Log4j 2, a logging library widely used in Java applications. It allows a remote attacker to execute arbitrary code on a vulnerable server or application.
Technical details:
- Impact: This vulnerability allows remote code execution (RCE) when malicious data is sent in a log parameter processed by Log4j 2. An attacker can exploit this vulnerability by sending a malicious text string that includes a Java Naming and Directory Interface (JNDI) query, which can remotely load and execute code.
- Attack Vector: The vulnerability is activated when Log4j 2 searches strings such as ${jndi:ldap://…} or other crafted URLs to load an object from a malicious server, allowing code execution.
- Affected Version: Log4j 2 versions 2.0 to 2.14.1.
- Severity: The attack can be exploited without prior authentication and is considered extremely dangerous due to its potential to allow arbitrary code execution in a wide variety of applications.
Protective measures:
- Update Log4j: The most effective solution is to update Log4j to version 2.15.0 or later, which fixes the vulnerability.
- Disable JNDI Lookup: A temporary workaround is to disable the JNDI lookup feature in vulnerable versions by setting the log4j2.formatMsgNoLookups system property to true.
- User Input Filtering: Limit data input and avoid the use of URLs in logs to prevent exploitation.
- Anomaly Monitoring and Detection: Use detection tools to identify abnormal behavior related to exploitation attempts.
Conclusion :
The CVE-2021-44228 vulnerability had a major impact due to the widespread use of Log4j in the Java ecosystem, exposing many applications and systems to a high risk of remote attack. It is essential to update or properly configure Log4j to protect against this threat.
