CVE-2026-23833
HIGH
GHSA-4h3h-63v6-88qx
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
3Description
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.
Analysis
ESPHome versions 2025.9.0 through 2025.12.6 are vulnerable to a denial-of-service attack via integer overflow in the API protobuf decoder, affecting all supported microcontroller platforms (ESP32, ESP8266, RP2040, LibreTiny). Unauthenticated attackers can crash ESPHome devices by sending specially crafted packets with large field length values to bypass bounds checking when API encryption is disabled. …
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Remediation
Within 7 days: Identify all affected systems running versions 2025.9.0 and apply vendor patches promptly. Vendor patch is available.
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