Apache Jackrabbit漏洞浅析
Apache Jackrabbit是一个Java开源内容存储库，1.0.0 <= 版本 < 2.20.11、2.21.0 <= 版本 < 2.21.18存在RMI功能导致的远程代码执行漏洞。
补丁分析
对比补丁前后两个版本（https://github.com/apache/jackrabbit/compare/jackrabbit-2.20.10...jackrabbit-2.20.11），基本只是删掉了CB库。
从官方文档（https://jackrabbit.apache.org/archive/wiki/JCR/RemoteAccess_115513494.html）可以知道存在RMI-over-HTTP的默认监听路径为/rmi。
在jackrabbit-standalone-components/src/main/resources/WEB-INF/web.xml中找到/rmi对应类：
RMI
/rmi
RMI
org.apache.jackrabbit.servlet.remote.RemoteBindingServlet
参考官方示例用URLRemoteRepository("http://localhost:8080/rmi");把Stub接下来，接口里的方法并不多，最接近Object的自然是Credentials。
Credentials是一个继承Serializable的空接口，我们看到4个实现之一的SimpleCredentials：
其中attributes属性是一个HashMap，有Object相关的setter/getter，要素齐全对接RMI反序列化CB的PriorityQueue就行，不需要知道用户密码。
newInstance0:-1, NativeConstructorAccessorImpl (sun.reflect)
newInstance:62, NativeConstructorAccessorImpl (sun.reflect)
newInstance:45, DelegatingConstructorAccessorImpl (sun.reflect)
newInstance:423, Constructor (java.lang.reflect)
newInstance:442, Class (java.lang)
getTransletInstance:455, TemplatesImpl (com.sun.org.apache.xalan.internal.xsltc.trax)
newTransformer:486, TemplatesImpl (com.sun.org.apache.xalan.internal.xsltc.trax)
getOutputProperties:507, TemplatesImpl (com.sun.org.apache.xalan.internal.xsltc.trax)
invoke0:-1, NativeMethodAccessorImpl (sun.reflect)
invoke:62, NativeMethodAccessorImpl (sun.reflect)
invoke:43, DelegatingMethodAccessorImpl (sun.reflect)
invoke:498, Method (java.lang.reflect)
invokeMethod:2128, PropertyUtilsBean (org.apache.commons.beanutils)
getSimpleProperty:1279, PropertyUtilsBean (org.apache.commons.beanutils)
getNestedProperty:809, PropertyUtilsBean (org.apache.commons.beanutils)
getProperty:885, PropertyUtilsBean (org.apache.commons.beanutils)
getProperty:464, PropertyUtils (org.apache.commons.beanutils)
compare:163, BeanComparator (org.apache.commons.beanutils)
siftDownUsingComparator:722, PriorityQueue (java.util)
siftDown:688, PriorityQueue (java.util)
heapify:737, PriorityQueue (java.util)
readObject:797, PriorityQueue (java.util)
invoke0:-1, NativeMethodAccessorImpl (sun.reflect)
invoke:62, NativeMethodAccessorImpl (sun.reflect)
invoke:43, DelegatingMethodAccessorImpl (sun.reflect)
invoke:498, Method (java.lang.reflect)
invokeReadObject:1170, ObjectStreamClass (java.io)
readSerialData:2178, ObjectInputStream (java.io)
readOrdinaryObject:2069, ObjectInputStream (java.io)
readObject0:1573, ObjectInputStream (java.io)
readObject:431, ObjectInputStream (java.io)
readObject:1409, HashMap (java.util)
invoke0:-1, NativeMethodAccessorImpl (sun.reflect)
invoke:62, NativeMethodAccessorImpl (sun.reflect)
invoke:43, DelegatingMethodAccessorImpl (sun.reflect)
invoke:498, Method (java.lang.reflect)
invokeReadObject:1170, ObjectStreamClass (java.io)
readSerialData:2178, ObjectInputStream (java.io)
readOrdinaryObject:2069, ObjectInputStream (java.io)
readObject0:1573, ObjectInputStream (java.io)
defaultReadFields:2287, ObjectInputStream (java.io)
readSerialData:2211, ObjectInputStream (java.io)
readOrdinaryObject:2069, ObjectInputStream (java.io)
readObject0:1573, ObjectInputStream (java.io)
readObject:431, ObjectInputStream (java.io)
unmarshalValue:322, UnicastRef (sun.rmi.server)
unmarshalParametersUnchecked:628, UnicastServerRef (sun.rmi.server)
unmarshalParameters:616, UnicastServerRef (sun.rmi.server)
dispatch:338, UnicastServerRef (sun.rmi.server)
run:200, Transport$1 (sun.rmi.transport)
run:197, Transport$1 (sun.rmi.transport)
doPrivileged:-1, AccessController (java.security)
serviceCall:196, Transport (sun.rmi.transport)
handleMessages:573, TCPTransport (sun.rmi.transport.tcp)
run0:834, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp)
lambda$run$0:688, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp)
run:-1, 679859895 (sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$14)
doPrivileged:-1, AccessController (java.security)
run:687, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp)
runWorker:1149, ThreadPoolExecutor (java.util.concurrent)
run:624, ThreadPoolExecutor$Worker (java.util.concurrent)
run:748, Thread (java.lang)