CVE-2026-23833
ESPHome vulnerable to denial-of-service via out-of-bounds check bypass in the API component
- State
- Published
- Severity
- 1.7 Low
- Published
- Jan 19, 2026
- Updated
- Jan 20, 2026
- Reserved
- Jan 16, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 1.7 Low | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U | GitHub_M |
Weaknesses
- CWE-190 Integer Overflow or Wraparound
Affected Products
| Product | Versions |
|---|---|
esphomeesphome |
|
References
Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.