Updated log4j libs due to CVE-2021-44228.

Change-Id: I8dc708089e0de0fa44d974b014f734dc6286a503
diff --git a/core/pom.xml b/core/pom.xml
index a645b00..917743d 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -13,7 +13,7 @@
 		<jetty.version>9.4.44.v20210927</jetty.version>
 		<hibernate.version>5.6.1.Final</hibernate.version>
 		<flyway.version>8.0.5</flyway.version>
-		<log4j.version>2.14.1</log4j.version>
+		<log4j.version>[2.15.0,)</log4j.version>
 		<krill.version>[0.60,)</krill.version>
 		<koral.version>[0.38,)</koral.version>
 	</properties>