CVE-2021-38540 — apache-airflow
CRITICALCVE-2021-38540 is a critical-severity (CVSS 9.8) Improper Privilege Management vulnerability in apache-airflow. 2 public exploit references exist, so weaponization risk is real. A fix is available for apache-airflow — see the affected versions and patch details below.
Missing Authentication for Critical Function in Apache Airflow
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2021-38540 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE sits: patch-first territory.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
apache-airflowReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | apache-airflow | ≥ 2.0.0&&< 2.1.3 | 2.1.3pip install --upgrade 'apache-airflow==2.1.3' |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for apache-airflow, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update apache-airflow to 2.1.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-38540 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-38540 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-38540. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
How to detect CVE-2021-38540
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2021-38540 -u https://target- Template
- Apache Airflow - Unauthenticated Variable Import
- Severity
- critical
- Impact
- An attacker can exploit this vulnerability to import malicious variables, potentially gaining unauthorized access to sensitive data.
- Remediation
- Upgrade to Apache Airflow 2.1.3 or higher.
Template by ProjectDiscovery nuclei-templates (pdteam), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2021-38540 in your dependencies?
O3 Security finds CVE-2021-38540 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.