CVE-2026-23833
highpriority · track · 30EPSS 0.003 · 23 %ileEUUSEPSS · scored 2026-10-27
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
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · low–high · 1.7–7.5
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (3)
Products and version ranges known to be affected.
advisories (2)
Vendor and ecosystem advisories describing this.
- GHSA-4h3h-63v6-88qxESPHome vulnerable to denial-of-service via out-of-bounds check bypass in the API component2026-01-21ghsa · osvUS
### 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](https://esphome.io/components/api.html#configuration-variables) with a unique key per device - Follow the [Security Best Practices](https://esphome.io/guides/security_best_practices/) ### Severity Low - Users following [Security Best Practices](https://esphome.io/guides/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](https://github.com/Mat931) for responsibly reporting this vulnerability.
- PYSEC-2026-1326ESPHome vulnerable to denial-of-service via out-of-bounds check bypass in the API component2026-07-07vendor · osvUS
### 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](https://esphome.io/components/api.html#configuration-variables) with a unique key per device - Follow the [Security Best Practices](https://esphome.io/guides/security_best_practices/) ### Severity Low - Users following [Security Best Practices](https://esphome.io/guides/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](https://github.com/Mat931) for responsibly reporting this vulnerability.
also known as (6)
Other names and identifiers for this entity.
sources
Which sources assert this record, and when.
references (13)
External citations — patches, advisories, analysis.
- https://esphome.io/guides/security_best_practicescnnvd
- https://github.com/esphome/esphome/commit/69d7b6e9210390051318bd8e6410727689de08d6cnnvd
- https://github.com/esphome/esphome/pull/13306cnnvd
- https://github.com/esphome/esphome/releasesPatchcnnvd
- https://github.com/esphome/esphome/security/advisories/GHSA-4h3h-63v6-88qxcnnvd
- https://esphome.io/guides/security_best_practicesenisa_euvd
- https://github.com/esphome/esphome/commit/69d7b6e9210390051318bd8e6410727689de08d6enisa_euvd
- https://github.com/esphome/esphome/pull/13306enisa_euvd
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