CVE-2021-41104

Name: CVE-2021-41104
Creator: NVD / NIST
Published: 2021-09-28T16:15:08.413+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 1.18%

Last modified Jun 17, 2026

CVE-2021-41104 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. ESPHome is a system to control the ESP8266/ESP32. Anyone with web_server enabled and HTTP basic auth configured on version 2021.9.1 or older is vulnerable to an issue in which `web_server` allows over-the-air (OTA) updates without checking user defined basic auth username & password. EPSS estimates a 1.18% chance of exploitation in the next 30 days.

Description

ESPHome is a system to control the ESP8266/ESP32. Anyone with web_server enabled and HTTP basic auth configured on version 2021.9.1 or older is vulnerable to an issue in which `web_server` allows over-the-air (OTA) updates without checking user defined basic auth username & password. This issue is patched in version 2021.9.2. As a workaround, one may disable or remove `web_server`.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

1.18%

63.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Esphome	Esphome Firmware	< 2021.9.2

References

https://github.com/esphome/esphome/pull/2409/commits/207cde1667d8c799a197b78ca8a5a14de8d5ca1ePatch, Third Party Advisory
https://github.com/esphome/esphome/releases/tag/2021.9.2Release Notes, Third Party Advisory
https://github.com/esphome/esphome/security/advisories/GHSA-48mj-p7x2-5jfmPatch, Third Party Advisory
https://github.com/esphome/esphome/pull/2409/commits/207cde1667d8c799a197b78ca8a5a14de8d5ca1ePatch, Third Party Advisory
https://github.com/esphome/esphome/releases/tag/2021.9.2Release Notes, Third Party Advisory
https://github.com/esphome/esphome/security/advisories/GHSA-48mj-p7x2-5jfmPatch, Third Party Advisory

Timeline

Published: Sep 28, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-41104?

How severe is CVE-2021-41104?

CVE-2021-41104 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.18% probability of exploitation in the next 30 days.

How do I fix CVE-2021-41104?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-41104?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST