CVE-2019-17571

A flaw was discovered in Log4j, where a vulnerable SocketServer class may lead to the deserialization of untrusted data. This flaw allows an attacker to remotely execute arbitrary code when combined with a deserialization gadget.

Mitigation

Please note that the Log4j upstream strongly recommends against using the SerializedLayout with the SocketAppenders. Customers may mitigate this issue by removing the SocketServer class outright; or if they must continue to use SocketAppenders, they can modify their SocketAppender configuration from SerializedLayout to use JsonLayout instead. An example of this in log4j-server.properties might look like this:

log4j.appender.file.layout=org.apache.log4j.JsonLayout