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.
Problem types
CWE-190: Integer Overflow or Wraparound
Product status
References
github.com/...sphome/security/advisories/GHSA-4h3h-63v6-88qx
github.com/esphome/esphome/pull/13306
github.com/...ommit/69d7b6e9210390051318bd8e6410727689de08d6
esphome.io/guides/security_best_practices