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CVE-2021-38540· NVD / CVE Program· CNA apache

Apache Airflow: Variable Import endpoint missed authentication check

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.

CriticalCVSS 9.8 · v3.1—Proof of concept Fix available
Published
Sep 9, 2021
Updated
Jun 17, 2026
EPSS
80.9% · 100th percentile
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Report tools

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Action score

63

This week

Don’t wait for the next maintenance window.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
24 / 30 · 80.9%

Affected systems

VendorProduct
apacheairflow

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • apache airflow2.0.0 and later · before 2.1.3

Versions reported by the vendor

Affected version ranges reported by the assigning authority (apache). Independent of NVD's CPE analysis and usually ahead of it.

  • Apache Software Foundation Apache Airflow

    • Apache Airflow and later · before 2.1.3affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
PyPIapache-airflowfrom 2.0.0 · before 2.1.32.1.3
PyPIapache-airflowfrom 2.0.0 · before 2.1.32.1.3

Same product

apache: all records

Other highest-scoring records for the same primary product.

  • CVE-2020-13927The previous default setting for Airflow's Experimental API was to allow all API requests without authentication, but this poses security riKEV
    99Now
  • CVE-2020-11978An issue was found in Apache Airflow versions 1.10.10 and below.KEV
    95Now
  • CVE-2022-40127Apache Airflow <2.4.0 has an RCE in a bash example
    61This week
  • CVE-2022-24288Apache Airflow: RCE in example DAGs
    58Plan
  • CVE-2020-11981An issue was found in Apache Airflow versions 1.10.10 and below.
    50Plan
  • CVE-2022-45402Apache Airflow: Open redirect during login
    49Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
PyPI:apache-airflow2.1.3Package registry (OSV)

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Nuclei detection template ×1
  • Proof-of-concept repository on GitHub ×1

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Nuclei detection templateNuclei template CVE-2021-38540 —
Proof-of-concept repository on GitHubstars:42022-06-13

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. First PoC+277 d
  3. TodaySep 29, 2026+1846 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-269 · Improper Privilege Management

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-primary

Root cause

To simplify setup, a service account is granted broad, cluster-wide permissions. The principle of least privilege is skipped during installation.

The bug in code

The whole CWE-269 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

yaml
kind: ClusterRolerules:  - apiGroups: ["*"]    resources: ["*"]    verbs: ["*"]

Fixed

yaml
kind: Rolemetadata:  namespace: lodos-systemrules:  - apiGroups: ["apps"]    resources: ["deployments"]    verbs: ["get", "list", "update"]

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Change log

  1. Fix✗ → ✓

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References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records