What’s Vulnerable › Vulnerabilities

CVE-2026-41016: Apache Airflow Providers SMTP: No certificate validation on SMTP STARTTLS connections in SMTP provider

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-30 · updated 2026-10-26
• Weakness: CWE-295

Description

Apache Airflow's SMTP provider `SmtpHook` called Python's `smtplib.SMTP.starttls()` without an SSL context, so no certificate validation was performed on the TLS upgrade. A man-in-the-middle between the Airflow worker and the SMTP server could present a self-signed certificate, complete the STARTTLS upgrade, and capture the SMTP credentials sent during the subsequent `login()` call. Users are advised to upgrade to the `apache-airflow-providers-smtp` version that contains the fix.

Affected products

• Apache Airflow: from 2.0.0 before 3.0.0 — fixed in 3.0.0

How to fix

Upgrade to a fixed version: Apache Airflow 3.0.0. Check the vendor advisory for mitigations.

References

• https://github.com/apache/airflow/pull/65346
• https://lists.apache.org/thread/gb202qy5r31bgdd3d51d7s5o1jh40kc4

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