# CVE-2021-26559: CWE-284 Improper Access Control on Configurations Endpoint for the Stable API

> Attackers with Viewer or User roles can access sensitive configuration data via the Stable API, bypassing intended access controls.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Feb 2021
- **Updated:** 13 Feb 2025
- **Also known as:** BIT-airflow-2021-26559, GHSA-ffw3-6mp6-jmvj, PYSEC-2021-2

## What is CVE-2021-26559?

CVE-2021-26559 is a medium-severity missing authorization vulnerability in Apache Airflow, published on 17 Feb 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Improper Access Control on Configurations Endpoint for the Stable API of Apache Airflow allows users with Viewer or User role to get Airflow Configurations including sensitive information even when `[webserver] expose_config` is set to `False` in `airflow.cfg`. This allowed a privilege escalation attack. This issue affects Apache Airflow 2.0.0.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2021-26559?

4 open source packages ship an affected version, including apache-airflow and airflow. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `apache-airflow` | PyPI | All versions | 2.0.1 |
| `apache-airflow` | PyPI | From 2.0.0 | 2.0.1rc1 |
| `apache-airflow` | PyPI | From 2.0.0 | 2.0.1rc1 |
| `airflow` | Bitnami | From 2.0.0 | 2.0.1 |

Products: Apache Airflow.

## How do I fix CVE-2021-26559?

Upgrade apache-airflow to a fixed version for your release line: 2.0.1 or 2.0.1rc1.

## Is CVE-2021-26559 being exploited?

There is no known exploitation of CVE-2021-26559 in the wild and no public exploit code.

## Other vulnerabilities in Apache Airflow

- [CVE-2020-13927](https://insights.sbomify.com/CVE-2020-13927/): Apache Airflow's Experimental API Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-11978](https://insights.sbomify.com/CVE-2020-11978/): Apache Airflow Command Injection (high 8.8, exploited in the wild)
- [CVE-2026-33264](https://insights.sbomify.com/CVE-2026-33264/): Apache Airflow: DAG author RCE on webserver via unrestricted import_string() in BaseSerialization.deserialize() (critical 9.8)
- [CVE-2023-25754](https://insights.sbomify.com/CVE-2023-25754/): Apache Airflow: Privilege escalation using airflow logs (critical 9.8)
- [CVE-2023-22884](https://insights.sbomify.com/CVE-2023-22884/): Apache Airflow, Apache Airflow MySQL Provider: Arbitrary file read via MySQL provider in Apache Airflow (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-26559 and fix it if it is affected.

What it is: CVE-2021-26559 is a medium-severity missing authorization vulnerability in Apache Airflow, published on 17 Feb 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-26559 in the wild and no public exploit code.

Affected packages and fixed versions:
- apache-airflow (PyPI): affected all versions; fixed in 2.0.1
- apache-airflow (PyPI): affected from 2.0.0; fixed in 2.0.1rc1
- apache-airflow (PyPI): affected from 2.0.0; fixed in 2.0.1rc1
- airflow (Bitnami): affected from 2.0.0; fixed in 2.0.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-26559/ (Markdown: https://insights.sbomify.com/CVE-2021-26559/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-26559
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-26559
- OSV: https://osv.dev/vulnerability/CVE-2021-26559

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-26559/
Summaries are generated and may contain mistakes; the official description above is the record.