Jenkins cannot reach nodes after upgrade

I just upgraded Jenkins from 2.39 to 2.57. After the upgrade, Jenkins can no longer communicate with my SSH build nodes. I get the following error:

channel started
Slave JVM has not reported exit code. Is it still running?
[04/28/17 01:29:32] Launch failed - cleaning up connection
[04/28/17 01:29:32] [SSH] Connection closed.
ERROR: Connection terminated
java.io.EOFException
    at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2335)
    at java.io.ObjectInputStream$BlockDataInputStream.readShort(ObjectInputStream.java:2804)
    at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:802)
    at java.io.ObjectInputStream.(ObjectInputStream.java:299)
    at hudson.remoting.ObjectInputStreamEx.(ObjectInputStreamEx.java:48)
    at hudson.remoting.AbstractSynchronousByteArrayCommandTransport.read(AbstractSynchronousByteArrayCommandTransport.java:34)
    at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:59)
Caused: java.io.IOException: Unexpected termination of the channel
    at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:73)

Based on Googling 'Slave JVM has not reported exit code.' it seems like a Java version mismatch (JENKINS-30561, JENKINS-29120), but I can confirm that my build nodes are using Java 1.7:

$ java -version
java version "1.7.0_80"
Java(TM) SE Runtime Environment (build 1.7.0_80-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.80-b11, mixed mode)

Does anyone have ideas what could be causing this? More info can be provided on request.

I found out via this StackOverflow question which pointed me to JENKINS-27624 which indicates that Java 8 is now required.

Update: I upgraded Java on all my nodes this morning and they are up and working.

StackExchange DevOps Q#1053, answer score: 5