FULL PRODUCT VERSION :
java version "1.8.0_66"
Java(TM) SE Runtime Environment (build 1.8.0_66-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.66-b17, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Linux <host> 2.6.32-573.8.1.el6.x86_64 #1 SMP Wed Nov 11 15:27:45 CET 2015 x86_64 x86_64 x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
Whenever the krb5.conf file has a comment starting with semicolon not in the beginning of file, for example:
[libdefaults]
 default_realm = EXAMPLE.COM
 ...
; comment
[realms]
 EXAMPLE.ORG = {
  ...
 }

When parsing the configuration, Java is throwing an exception:
KrbException: Illegal config content:; comment
at sun.security.krb5.Config.parseStanzaTable(Config.java:609)
at sun.security.krb5.Config.<init>(Config.java:177)
at sun.security.krb5.Config.getInstance(Config.java:98)
... 9 more

While checking the source code of Kerberos (the latest version), you can see that semicolon is a valid comment starting character. Check prof_parce.c file in src/util/profile directory.

Other sources suggest that semicolon should be accepted as comment starting character:
https://groups.google.com/forum/#!topic/comp.protocols.kerberos/i_Cl2d7TLGU


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The krb5.conf file with semicolons should be parsed successfully.
ACTUAL -
Exception is being thrown:
KrbException: Illegal config content:; comment
at sun.security.krb5.Config.parseStanzaTable(Config.java:609)
at sun.security.krb5.Config.<init>(Config.java:177)
at sun.security.krb5.Config.getInstance(Config.java:98)
... 9 more

ERROR MESSAGES/STACK TRACES THAT OCCUR :
KrbException: Illegal config content:; comment
at sun.security.krb5.Config.parseStanzaTable(Config.java:609)
at sun.security.krb5.Config.<init>(Config.java:177)
at sun.security.krb5.Config.getInstance(Config.java:98)
... 9 more

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
Taken from Hadoop source code:


    Object kerbConf;
    Class<?> classRef;
    Method getInstanceMethod;
    Method getDefaultRealmMethod;
    if (IBM_JAVA) {
      classRef = Class.forName("com.ibm.security.krb5.internal.Config");
    } else {
      classRef = Class.forName("sun.security.krb5.Config");
    }
    getInstanceMethod = classRef.getMethod("getInstance", new Class[0]);
    kerbConf = getInstanceMethod.invoke(classRef, new Object[0]);
    getDefaultRealmMethod = classRef.getDeclaredMethod("getDefaultRealm",
         new Class[0]);
    return (String)getDefaultRealmMethod.invoke(kerbConf, new Object[0]);
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Removing the comment starting with semicolon or replacing semicolon by #.