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CVE-2021-41104

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`.

Security Impact Summary

This vulnerability carries a HIGH severity rating with a CVSS v3.1 score of 7.5, indicating it can be exploited remotely over the network with relatively low complexity without requiring user interaction and does not require pre-existing privileges . The vulnerability impacts integrity (unauthorized modifications), for affected systems. Impacting 3 products from esphome, from espressif, from espressif organizations running these solutions should prioritize assessment and patching.

Historical Context

Reported in 2021, this vulnerability emerged during an era marked by increased sophistication in supply chain attacks, cloud infrastructure vulnerabilities, and software-as-a-service (SaaS) security challenges. Security practices during this period emphasized zero-trust architectures, container security, and API protection.

Published

2021-09-28T16:15:08.413

Last Modified

2026-06-17T04:07:52.940

Status

Modified

Source

[email protected]

Severity

CVSSv3.1: 7.5 (HIGH)

CVSSv2 Vector

AV:N/AC:M/Au:N/C:N/I:P/A:N

Access Vector: NETWORK
Access Complexity: MEDIUM
Authentication: NONE
Confidentiality Impact: NONE
Integrity Impact: PARTIAL
Availability Impact: NONE

Exploitability Score

8.6

Impact Score

2.9

Weaknesses

Type: Secondary
CWE-306
Type: Primary
CWE-306

Affected Vendors & Products

Type	Vendor	Product	Version/Range	Vulnerable?
Operating System	esphome	esphome_firmware	< 2021.9.2	Yes
Hardware	espressif	esp32	-	No
Hardware	espressif	esp8266	-	No

References

https://github.com/esphome/esphome/pull/2409/commits/207cde1667d8c799a197b78ca8a5a14de8d5ca1e Patch, Third Party Advisory ([email protected])
https://github.com/esphome/esphome/releases/tag/2021.9.2 Release Notes, Third Party Advisory ([email protected])
https://github.com/esphome/esphome/security/advisories/GHSA-48mj-p7x2-5jfm Patch, Third Party Advisory ([email protected])
https://github.com/esphome/esphome/pull/2409/commits/207cde1667d8c799a197b78ca8a5a14de8d5ca1e Patch, Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://github.com/esphome/esphome/releases/tag/2021.9.2 Release Notes, Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://github.com/esphome/esphome/security/advisories/GHSA-48mj-p7x2-5jfm Patch, Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)

How SecUtils Interprets This CVE

SecUtils normalizes and enriches National Vulnerability Database (NVD) records by standardizing vendor and product identifiers, aggregating vulnerability metadata from both NVD and MITRE sources, and providing structured context for security teams. For esphome's affected products, we extract Common Platform Enumeration (CPE) data, Common Weakness Enumeration (CWE) classifications, CVSS severity metrics, and reference data to enable rapid vulnerability prioritization and asset correlation. This record contains no exploit code, proof-of-concept instructions, or attack methodologies—only defensive intelligence necessary for patch management, risk assessment, and security operations.