CVE-2026-71260 in ESPHome
Summary
by MITRE • 08/05/2026
ESPHome through 2026.7.0-dev discloses plaintext passwords via its web_server component. In WebServer::text_json_() (esphome/components/web_server/web_server.cpp), a text entity configured with mode: password (TEXT_MODE_PASSWORD) has its JSON "state" field correctly masked as "********", but the same serialization path unconditionally writes the raw password into the JSON "value" field via set_json_icon_state_value()/set_json_value(). Because web_server listens on port 80 with no authentication by default, any attacker on the local network can retrieve the plaintext password (e.g. WiFi credentials, API tokens) via GET /text/<entity_id> or the /events EventSource stream.
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Analysis
by VulDB Data Team • 08/05/2026
The vulnerability in ESPHome versions up to 2026.7.0-dev represents a critical security flaw in the web_server component that exposes plaintext passwords through improper data serialization practices. This issue affects devices running the ESPHome firmware where the web_server component operates on port 80 without authentication by default, creating an attack surface accessible to any local network user. The vulnerability specifically targets text entities configured with mode: password which are intended to protect sensitive credentials such as WiFi passwords, API tokens, and other authentication data.
The technical flaw occurs within the WebServer::text_json_() function located in esphome/components/web_server/web_server.cpp where the system correctly masks the "state" field as "****" for security purposes but fails to apply the same protection to the "value" field. This inconsistency stems from the unconditional writing of raw password data into the JSON "value" field through the set_json_icon_state_value() and set_json_value() functions. The serialization process treats all text entities uniformly regardless of their configured security mode, effectively bypassing the intended protection mechanisms.
The operational impact of this vulnerability is severe as it allows attackers on the local network to obtain plaintext credentials simply by making GET requests to /text/<entity_id> endpoints or by consuming the /events EventSource stream. This means that any device running ESPHome with the default web_server configuration becomes a potential vector for credential theft, particularly in environments where network segmentation is not properly implemented. The exposure of WiFi credentials could enable attackers to gain network access, while API tokens might provide unauthorized access to connected services and IoT ecosystems.
Security implications extend beyond immediate credential exposure as this vulnerability aligns with CWE-200 (Information Exposure) and represents a failure in proper input validation and output encoding practices. The issue also relates to ATT&CK technique T1566 (Phishing) and T1078 (Valid Accounts) where attackers can leverage stolen credentials to establish persistent access. Organizations using ESPHome devices should immediately implement network segmentation, disable unnecessary web_server components, or configure authentication mechanisms to prevent unauthorized access to these endpoints. The vulnerability demonstrates the importance of consistent security controls across all data serialization paths and highlights the need for proper configuration management in IoT device deployments where default insecure settings can lead to significant compromise opportunities.