CVE-2026-23833 — HIGH (7.5)

Q: How severe is CVE-2026-23833?

CVE-2026-23833 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.

Q: Is there a patch for CVE-2026-23833?

Check the references section above for vendor advisories and patch information. Affected products include: Esphome Esphome.

Vulnerability Description

ESPHome is a system to control microcontrollers remotely through Home Automation systems. In versions 2025.9.0 through 2025.12.6, an integer overflow in the API component's protobuf decoder allows denial-of-service attacks when API encryption is not used. The bounds check `ptr + field_length > end` in `components/api/proto.cpp` can overflow when a malicious client sends a large `field_length` value. This affects all ESPHome device platforms (ESP32, ESP8266, RP2040, LibreTiny). The overflow bypasses the out-of-bounds check, causing the device to read invalid memory and crash. When using the plaintext API protocol, this attack can be performed without authentication. When noise encryption is enabled, knowledge of the encryption key is required. Users should upgrade to ESPHome 2025.12.7 or later to receive a patch, enable API encryption with a unique key per device, and follow the Security Best Practices.

CVSS Score

7.5

HIGH

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

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality

NONE

Integrity

NONE

Availability

HIGH

Affected Products

Vendor	Product	Versions
Esphome	Esphome	>= 2025.9.0, < 2025.12.7

Related Weaknesses (CWE)

CWE-190

References

https://esphome.io/guides/security_best_practicesTechnical Description
https://github.com/esphome/esphome/commit/69d7b6e9210390051318bd8e6410727689de08Patch
https://github.com/esphome/esphome/pull/13306Issue TrackingPatch
https://github.com/esphome/esphome/security/advisories/GHSA-4h3h-63v6-88qxMitigationPatchVendor Advisory

FAQ

What is CVE-2026-23833?

CVE-2026-23833 is a vulnerability with a CVSS score of 7.5 (HIGH). ESPHome is a system to control microcontrollers remotely through Home Automation systems. In versions 2025.9.0 through 2025.12.6, an integer overflow in the API component's protobuf decoder allows den...

How severe is CVE-2026-23833?

CVE-2026-23833 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-23833?

Check the references section above for vendor advisories and patch information. Affected products include: Esphome Esphome.