Apache Airflow has no certificate validation on SMTP STARTTLS connections
Medium5.9CVE-2026-49267 · Published Jun 1, 2026 · updated Jul 13, 2026
Apache Airflow's EmailOperator and the underlying `airflow.utils.email` helpers established SMTP STARTTLS connections without verifying the remote certificate when the deployment used `[email] smtp_starttls=True` without `[email] smtp_ssl`. An attacker positioned between the worker and the configured SMTP server (network MITM , typical hostile-network attack-surface for environments where the SMTP relay sits outside the worker's trust boundary) could present a self-signed certificate, have the worker complete the STARTTLS handshake silently, and capture the SMTP AUTH credentials and message contents the worker forwarded. This CVE covers the **core apache-airflow side** of the same root cause already covered for the SMTP provider by `CVE-2026-41016` (published 2026-04-27, covering `apache-airflow-providers-smtp`). Users who already applied the SMTP-provider fix from CVE-2026-41016 should additionally upgrade `apache-airflow` to 3.2.2 or later to cover the core-side path through `airflow.utils.email`. Affects deployments configured with `smtp_starttls=True` and `smtp_ssl=False` where the SMTP relay is reachable across a less-trusted network segment than the worker. Users are advis...
Affected versions
| Package | Affected | Fixed in |
|---|---|---|
| apache-airflow PyPI | >= 2.0.0, < 3.2.2 | 3.2.2 |
Details and references
Apache Airflow's EmailOperator and the underlying `airflow.utils.email` helpers established SMTP STARTTLS connections without verifying the remote certificate when the deployment used `[email] smtp_starttls=True` without `[email] smtp_ssl`. An attacker positioned between the worker and the configured SMTP server (network MITM , typical hostile-network attack-surface for environments where the SMTP relay sits outside the worker's trust boundary) could present a self-signed certificate, have the worker complete the STARTTLS handshake silently, and capture the SMTP AUTH credentials and message contents the worker forwarded. This CVE covers the **core apache-airflow side** of the same root cause already covered for the SMTP provider by `CVE-2026-41016` (published 2026-04-27, covering `apache-airflow-providers-smtp`). Users who already applied the SMTP-provider fix from CVE-2026-41016 should additionally upgrade `apache-airflow` to 3.2.2 or later to cover the core-side path through `airflow.utils.email`. Affects deployments configured with `smtp_starttls=True` and `smtp_ssl=False` where the SMTP relay is reachable across a less-trusted network segment than the worker. Users are advised to upgrade to `apache-airflow` 3.2.2 or later.
- CVSS 3.1
- CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
- Severity from
- GitHub (reviewed advisory)
- Weakness
- CWE-295
- Also known as
- BIT-airflow-2026-49267, CVE-2026-49267, PYSEC-2026-2346
More Apache Airflow advisories
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|---|---|---|---|
| Jun 1 | Apache Airflow has an Authorization Bypass Through User-Controlled Key Medium4.3Jun 1 | Medium4.3 | 3.2.2 |
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| Jun 1 | Apache Airflow Vulnerable to Deserialization of Untrusted DataHigh7.3Jun 1 | High7.3 | 3.2.2 |
| Jun 1 | Apache Airflow Vulnerable to Exposure of Sensitive Information to an Unauthorized ActorMedium6.5Jun 1 | Medium6.5 | 3.2.2 |
| Jun 1 | Apache Airflow vulnerable to Improper Neutralization of Special Elements Used in a Template EngineCritical9.1Jun 1 | Critical9.1 | 3.2.2 |
| Jun 1 | Apache Airflow vulnerable to Exposure of Sensitive Information to an Unauthorized ActorMedium6.5Jun 1 | Medium6.5 | 3.2.2 |