Description

A severe weakness in ESPHome's ESP-IDF web server module, tracked as CVE-2025-57808, enables malicious actors on the same local network to bypass HTTP Basic Authentication and manipulate smart devices with no legitimate credentials. The weakness was uncovered by security researcher jesserockz and is a result of the way the AsyncWebServerRequest authenticate function processes the Authorization header—accepting empty or cut values and comparing just the early bytes rather than the entire credential string. The bug is in ESPHome version 2025.8.0, which allows unauthorized users to access protected endpoints by sending partial or even single-character credentials. Suppose the actual login is user:somereallylongpass; an attacker could gain unauthorized access using only s, some, or an empty string in the Authorization header. This broken comparison logic causes the server to send back an HTTP 200 OK, mistakenly deeming the request as authenticated. The effect is considerable. Local network attackers can carry out activities like initiating over-the-air (OTA) firmware updates, retrieving sensitive configuration information, or altering device settings without the user's permission. Because most smart home devices run inside private LANs, attackers can take advantage of the vulnerability by using ARP spoofing or other local network attacks to penetrate. To reduce security vulnerabilities, users should upgrade to ESPHome version 2025.8.1. Until this is patched, it's highly advisable to turn off the web_server component, limit local network access via firewalls or VLANs, and turn off OTA updates through the web UI. Though network segmentation decreases exposure, installing the patch is the sole surefire method.