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Vulnerability · Published Jan 19, 2026 · Assigned by GitHub_M

CVE-2026-23833ESPHome vulnerable to denial-of-service via out-of-bounds check bypass in the API component

Low 1.7

In plain English

A low-severity integer overflow in esphome from esphome. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 23% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)1.7Low
Exploit odds (30 days)0.3%top 77.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
PyPIesphome2025.12.7GHSA-4h3h-63v6-88qx
PyPIesphome2025.12.7PYSEC-2026-1326

Affected products (as reported)

VendorProductVersions
esphome esphome >= 2025.9.0, < 2025.12.7

Weakness: CWE-190 · Vector: 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

References