CVE-2026-41016Network attack vector

SMTP credential theft via unvalidated STARTTLS certificate

Published Apr 30, 2026 · Updated Apr 30, 2026

Improper certificate validation in Apache Airflow SMTP Provider 2.0.0 through 2.x allows man-in-the-middle attackers to steal SMTP credentials. The SmtpHook sync and async connection paths pass no SSL context to starttls(), causing the TLS upgrade to accept an untrusted certificate before login(). Exploitation requires a network position between an Airflow worker and its SMTP server; it exposes credentials but does not alter data or interrupt service.

CVSS severity5.9
Medium
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in Apache Airflow SMTP Provider 2.0.0 through 2.x allows man-in-the-middle attackers to steal SMTP credentials. The SmtpHook sync and async connection paths pass no SSL context to starttls(), causing the TLS upgrade to accept an untrusted certificate before login(). Exploitation requires a network position between an Airflow worker and its SMTP server; it exposes credentials but does not alter data or interrupt service.

The record

CVE
CVE-2026-41016
Published
Apr 30, 2026
Updated
Apr 30, 2026
Vendor
The Apache Software Foundation
Product
Apache Airflow SMTP Provider
Classifications
CWE-295, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 30, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 30, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.0.0 <3.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Airflow SMTP Providerversion=2.0.0 <3.0.0

Published CVSS scores

5.9CISA-ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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