A important safety vulnerability found in ESPHome’s internet server part has uncovered hundreds of good residence gadgets to unauthorized entry, successfully nullifying primary authentication protections on ESP-IDF platform implementations.
The flaw, designated CVE-2025-57808 with a CVSS rating of 8.1, impacts ESPHome model 2025.8.0 and permits attackers to bypass authentication mechanisms with none information of authentic credentials.
The vulnerability stems from a basic logic error within the HTTP primary authentication verify inside ESPHome’s web_server_idf part.
When processing authentication requests, the system’s AsyncWebServerRequest::authenticate operate solely compares bytes as much as the size of the client-supplied authorization worth, relatively than validating the whole credential string.
This implementation flaw creates two distinct assault vectors that utterly compromise system safety.
Essentially the most extreme facet of this vulnerability entails empty authorization headers, the place attackers can achieve full entry by merely sending a request with Authorization: Fundamental adopted by an empty string.
GitHub analysts recognized that this assault vector requires no prior information of usernames or passwords, making it significantly harmful for network-adjacent attackers.
Moreover, the flaw accepts partial password matches, that means an attacker who discovers even a substring of the proper password can efficiently authenticate.
Assault Mechanism and Technical Exploitation
The vulnerability’s technical basis lies within the improper string comparability logic that processes base64-encoded credentials.
When a authentic system is configured with credentials like person:somereallylongpass (encoded as dXNlcjpzb21lcmVhbGx5bG9uZ3Bhc3M=), the flawed authentication verify accepts shorter strings comparable to dXNlcjpz (representing person:s) as legitimate credentials.
Sensible exploitation requires minimal technical sophistication. Attackers can make the most of easy curl instructions to exhibit the vulnerability:-
curl -D- -H ‘Authorization: Fundamental ‘
This command bypasses authentication fully, returning HTTP 200 responses as an alternative of the anticipated 401 Unauthorized standing.
The vulnerability turns into significantly regarding when Over-The-Air (OTA) replace performance is enabled, as attackers achieve full management over system firmware and configuration settings.
ESPHome addressed this important flaw in model 2025.8.1, implementing correct credential validation that compares full authorization strings relatively than partial matches.
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