ESPHome vulnerable to denial-of-service via out-of-bounds check bypass in the API component
Summary
An integer overflow in the API component's protobuf decoder allows denial-of-service attacks when API encryption is not used.
Details
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.
Affected Versions
ESPHome 2025.9.0 through 2025.12.6
Mitigation
- Upgrade to ESPHome 2025.12.7 or later (or 2026.1.0b3 or later)
- Enable API encryption with a unique key per device
- Follow the Security Best Practices
Severity
Low - Users following Security Best Practices with API encryption enabled are not affected without knowledge of the encryption key.
Impact
Denial-of-service. An attacker with network access to port 6053 can crash and reboot the device.
Credits
Thanks to @Mat931 for responsibly reporting this vulnerability.
Software afectado
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| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Python (PyPI) | esphome | >= 2025.9.0, < 2025.12.7 | 2025.12.7 |
Referencias
- https://github.com/esphome/esphome/security/advisories/GHSA-4h3h-63v6-88qx
- https://nvd.nist.gov/vuln/detail/CVE-2026-23833
- https://github.com/esphome/esphome/pull/13306
- https://github.com/esphome/esphome/commit/69d7b6e9210390051318bd8e6410727689de08d6
- https://esphome.io/guides/security_best_practices
- https://github.com/esphome/esphome
- https://pypi.org/project/esphome
- https://github.com/advisories/GHSA-4h3h-63v6-88qx
- Vector CVSS
CVSS:4.0/AV:A/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N- Debilidad (CWE)
CWE-190- Plataforma
- Python (PyPI)
- Paquete
esphome- Publicada
- 21.01.2026
- Actualizado
- 11.10.2026 13:18
Fuentes y licencias
OSV / GitHub Advisory Database - PYSEC-2026-1326 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-4h3h-63v6-88qx - CC BY 4.0
Historial de vulnerabilidades: esphome
Todas las vulnerabilidades publicadas de este paquete (Python (PyPI)), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.
- Entradas en total
- 6
- Primera → última
- 09.2021 01.2026
- Sin corrección
- 0
- Explotada en ataques
- 0
Distribución por gravedad
- Alta 4
- Media 2
Divulgaciones por año
- 2021: 1
- 2022: 0
- 2023: 0
- 2024: 3
- 2025: 1
- 2026: 1
-
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