CVE-2021-41104

mediumpriority · track · 30OT risk · elevatedEPSS 0.012 · 68 %ileEUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

1.21% (68th) EPSS

CVSS 4.3 · medium

Is it mine?

3 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · osv · nvd

EPSS · scored 2026-10-27

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`.

cvss

Technical severity, 0–10. One row per scoring source.

7.5

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 4.3–7.5

v2.04.3mediumAV:N/AC:M/Au:N/C:N/I:P/A:Nprimary · NVD / NIST USexploitability 8.6 · impact 2.9

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:Nprimary · NVD / NIST USexploitability 3.9 · impact 3.6

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:Nsecondary · ENISA EU

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:Nsecondary · security-advisories@github.comexploitability 3.9 · impact 3.6

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:Nsecondary · OSV

v3.16.9mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-306USprimaryCWE-306US

affected products (3)

Products and version ranges known to be affected.

esphome esphome≤ < 2021.9.2enisa_euvdEU
esphome esphome firmware< 2021.9.2nvdUScpe:2.3:o:esphome:esphome_firmware:*:*:*:*:*:*:*:*
PyPI esphome< 2021.9.2osvUSpkg:pypi/esphome

advisories (2)

Vendor and ecosystem advisories describing this.

GHSA-48mj-p7x2-5jfmBasic auth bypass in esphome2021-09-29ghsa · osvUS
### Impact Anyone with web_server enabled and HTTP basic auth configured on 2021.9.1 or older `web_server` allows OTA update without checking user defined basic auth username & password ### Patches Patch released in 2021.9.2 ### Workarounds Disable/remove `web_server`
PYSEC-2021-3512021-09-28vendor · osvUS
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`.

also known as (6)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd osv nvd NVD CVE.org MITRE

published 2021-09-28modified 2026-06-17

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+4460 more

references (10)

External citations — patches, advisories, analysis.

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