| Shelly Plug S
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Security Grade
Calculator v1
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Shelly Plug S
Category: Smart Plug • Model / Gen: Shelly Plug S (SHPLG-S)
Release Date: 2020-06-01 • Status: End of sale
Classification Date: 2026-10-21
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Security Evaluation
1. Device Security
| Criterion
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Value
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Proof
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Comment
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| Known hardware tampering
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Rare
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—
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Published Shelly findings are local/adjacent-network issues such as cleartext Wi-Fi credentials during setup on the TRV (CVE-2023-42144); no mass physical-tampering case for the Plug S.
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| Known vulnerabilities
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Rare
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—
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CVEs exist for the Shelly ecosystem (app firmware-update information leak, CVE-2024-48776; Pro 4PM resource exhaustion, CVE-2025-11243) but no Plug S specific advisory was found, hence Rare rather than Very common.
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| Prior attacks
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None
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No Shelly product appears in CISA KEV and no public attack campaign against the Plug S was identified.
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| Updatability
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Very common
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—
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Firmware is upgradeable OTA from the app or the local web UI, and Shelly publishes firmware archives per device generation.
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| Category Score
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Score: 2 / 3
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2. System Security
| Criterion
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Value
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Proof
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Comment
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| Authentication with other systems
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Full
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Device authenticates to the Shelly Cloud with a per-device token and can also be integrated via MQTT/Home Assistant with scoped credentials.
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| Communications
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Encrypted with up-to-date encryption
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Cloud and app traffic is TLS with certificate validation; local API can be switched to HTTPS/authenticated mode.
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| Storage
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Encrypted with up-to-date encryption
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Wi-Fi credentials and cloud tokens are stored in protected flash and are not readable through the documented API; no user content is stored.
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| Category Score
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Score: 1 / 3
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3. User Authentication
| Criterion
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Value
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Proof
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Comment
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| Account management
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Full
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Shelly account manages rooms, sharing and device ownership transfer, with the local web UI protected by a device password.
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| Authentication
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Basic
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Account password plus device-level password for the local UI; no enforced MFA on the plug itself.
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| Brute-force protection
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Basic
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Cloud login is rate limited; the local web UI has no configurable lockout after failed attempts.
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| Event logging
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Partial logging
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Device keeps switch/energy history and can emit events to MQTT, but there is no authentication audit log.
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| Passwords
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Require change after setup with complexity requirements
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The device password must be set at commissioning (no default) and the cloud account enforces complexity.
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| Category Score
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Score: 2 / 3
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Technical Specifications
| Property
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Details
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| Operating System & App
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Shelly embedded firmware (ESP8266 class) (Companion App: Shelly Smart Control app / local web UI)
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| Hardware (CPU / GPU)
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CPU: • GPU:
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| Memory & Storage
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Memory: • Storage: Onboard flash for configuration and schedules
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| Power, Battery & Charging
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Battery: • Power: AC 230 V, max 2500 W • Charging:
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| Display & Camera
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Display: • Camera:
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| Sound & Connectivity
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Sound: • Connectivity: 2.4 GHz Wi-Fi, Bluetooth (newer firmware), local HTTP/RPC API, MQTT
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| Physical (Dimensions & Mass)
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Dimensions: • Mass:
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Reasoning: Shelly devices are designed around local-first control with no mandatory cloud dependency, which removes a large class of consumer-IoT risk: pairing requires setting a device password and cloud tokens are per-device. The CVE record for the Shelly ecosystem is small and no Plug S specific issue was found, but the platform also enforces no MFA and has almost no authentication logging. Scope note: rated for a current firmware plug used with the local API or Shelly Cloud; exposing the local HTTP API without a password would lower the system criteria sharply. The non-Pro Plug S has been superseded by the Plus/Gen3 line and is assessed as end of sale.
