What vulnerability does Log4j exploit?

• A. Cross-site scripting
• B. Buffer overflow
• C. SQL injection
• D. Remote code execution

Answer: (D)

Log4j’s vulnerability is about remote code execution. The flaw comes from how Log4j processes log messages and supports JNDI lookups. An attacker can craft a log entry that triggers a JNDI lookup to a remote LDAP/LDAPS server you control. That server can then supply a Java class that Log4j loads and executes, giving the attacker arbitrary code on the affected server. This is a server-side compromise, not something that runs in a user's browser or alters input to a SQL query, so it’s not cross-site scripting, a buffer overflow, or SQL injection. The defining capability here is that an attacker can cause the application to run their code remotely via the vulnerable logging path.