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Public proof of conceptFix available

CVE-2021-38540

A public proof of concept exists; no exploitation attested.

  • Published2021-09-09
  • Fixed in2.1.3
  • WeaknessCWE-269 · CWE-306

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2021-09-0915:15CVE publishedNVD
  2. 2026-10-2319:23First public proof of conceptPoC-in-GitHub
  3. 2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-38540?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-38540?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV
Apache airflow
BranchAffectedFixed in
2.x≥ 2.0.0, < 2.1.32.1.3

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update Apache airflow to 2.1.3

Advisories and patches

Detection

read 2026-10-23 19:23 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
1 repository, unverifiedCaptain-v-hook/PoC-for-CVE-2021-38540-
PoC-in-GitHub

Sources

  • NVDCVSS 3.19.8read 2026-10-23
  • NVDCVSS 2.07.5read 2026-10-23
  • CNAweakness (CWE)CWE-269read 2026-10-23
  • NVDweakness (CWE)CWE-306read 2026-10-23
  • FIRST EPSSEPSS score80.9 %read 2026-10-23
  • PoC-in-GitHubproof of concept1read 2026-10-23
  • OSVaffected packages—

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2021-09-09
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2021-38540?

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.

Is CVE-2021-38540 actively exploited?

Active exploitation of CVE-2021-38540 has not been confirmed. Its EPSS score was 80.9% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-38540?

CVE-2021-38540 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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