CVE-2020-13927: Apache Airflow's Experimental API Authentication Bypass

Vulnerability summary

CVE-2020-13927 is a critical (CVSS 9.8) vulnerability in Apache Airflow's Experimental API. It is known to be exploited: CISA lists it, first on 18-01-2022. EPSS estimates a 99.78% chance of exploitation in the next 30 days, higher than 99.9% of scored vulnerabilities. 4 public exploits are recorded.

Timeline

1. 10-11-2020
   PublishedVulnerability first disclosed.
2. 18-01-2022
   Added to CISA KEVApache Airflow's Experimental API Authentication Bypass
3. 18-07-2022
   CISA remediation dueApply updates per vendor instructions.
4. 21-10-2025
   Last modifiedVulnerability information updated.

Description

The previous default setting for Airflow's Experimental API was to allow all API requests without authentication, but this poses security risks to users who miss this fact. From Airflow 1.10.11 the default has been changed to deny all requests by default and is documented at https://airflow.apache.org/docs/1.10.11/security.html#api-authentication. Note this change fixes it for new installs but existing users need to change their config to default `[api]auth_backend = airflow.api.auth.backend.deny_all` as mentioned in the Updating Guide: https://github.com/apache/airflow/blob/1.10.11/UPDATING.md#experimental-api-will-deny-all-request-by-default

• CWE-306Missing Authentication for Critical FunctionThe product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.
• CWE-1188Initialization of a Resource with an Insecure DefaultThe product initializes or sets a resource with a default that is intended to be changed by the product's installer, administrator, or maintainer, but the default is not secure.
• CWE-1056Invokable Control Element with Variadic ParametersA named-callable or method control element has a signature that supports a variable (variadic) number of parameters or arguments.