diff --git a/CHANGES.txt b/CHANGES.txt
index a529423f35..109cff75fe 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -8,6 +8,7 @@
  * org.apache.cassandra.db.rows.ArrayCell#unsharedHeapSizeExcludingData includes data twice (CASSANDRA-16900)
  * Exclude Jackson 1.x transitive dependency of hadoop* provided dependencies (CASSANDRA-16854)
 Merged from 3.11:
+ * Update Jackson from 2.9.10 to 2.12.5 (CASSANDRA-16851)
  * Make assassinate more resilient to missing tokens (CASSANDRA-16847)
 Merged from 3.0:
  * Make the addition of regular column to COMPACT tables throw an InvalidRequestException (CASSANDRA-14564)
diff --git a/build.xml b/build.xml
index c3f0746369..f519547054 100644
--- a/build.xml
+++ b/build.xml
@@ -516,9 +516,9 @@
           <dependency groupId="org.slf4j" artifactId="jcl-over-slf4j" version="1.7.25" />
           <dependency groupId="ch.qos.logback" artifactId="logback-core" version="1.2.3"/>
           <dependency groupId="ch.qos.logback" artifactId="logback-classic" version="1.2.3"/>
-          <dependency groupId="com.fasterxml.jackson.core" artifactId="jackson-core" version="2.9.10"/>
-          <dependency groupId="com.fasterxml.jackson.core" artifactId="jackson-databind" version="2.9.10.8"/>
-          <dependency groupId="com.fasterxml.jackson.core" artifactId="jackson-annotations" version="2.9.10"/>
+          <dependency groupId="com.fasterxml.jackson.core" artifactId="jackson-core" version="2.12.5"/>
+          <dependency groupId="com.fasterxml.jackson.core" artifactId="jackson-databind" version="2.12.5"/>
+          <dependency groupId="com.fasterxml.jackson.core" artifactId="jackson-annotations" version="2.12.5"/>
           <dependency groupId="com.googlecode.json-simple" artifactId="json-simple" version="1.1"/>
           <dependency groupId="com.boundary" artifactId="high-scale-lib" version="1.0.6"/>
           <dependency groupId="com.github.jbellis" artifactId="jamm" version="${jamm.version}"/>
diff --git a/src/java/org/apache/cassandra/cql3/Json.java b/src/java/org/apache/cassandra/cql3/Json.java
index ea0a49ccba..d05096a397 100644
--- a/src/java/org/apache/cassandra/cql3/Json.java
+++ b/src/java/org/apache/cassandra/cql3/Json.java
@@ -42,6 +42,7 @@ public class Json
      */
     public static String quoteAsJsonString(String s)
     {
+        // In future should update to directly use `JsonStringEncoder.getInstance()` but for now:
         return new String(BufferRecyclers.getJsonStringEncoder().quoteAsString(s));
     }