What’s Vulnerable › Vulnerabilities

CVE-2026-64823: Home Assistant Core < 2026.5.4 XSS via Shelly media_player.py thumb URI

• Severity: medium (CVSS 4.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-21 · updated 2026-10-24
• Weakness: CWE-79

Description

Home Assistant Core before 2026.5.4 contains a cross-site scripting vulnerability in the Shelly integration's async_get_media_image() method that allows attackers controlling a Shelly device's thumb field to serve arbitrary HTML content by supplying a data URI with a text/html content type without validation against an image-only allowlist. Attackers can cause the media player proxy endpoint to serve attacker-controlled bytes with Content-Type text/html in the Home Assistant web origin, enabling theft of session tokens from local storage and authenticated calls to sensitive service endpoints including lock, alarm, and cover controls.

Affected products

• home-assistant Home Assistant Core: before 2026.5.4 — fixed in 2026.5.4

How to fix

Upgrade to a fixed version: home-assistant Home Assistant Core 2026.5.4. Check the vendor advisory for mitigations.

References

• https://github.com/home-assistant/core/commit/894a68acb678afc382fe5ea9002e61ab7f862011
• https://github.com/home-assistant/core/pull/171585
• https://github.com/home-assistant/core/releases/tag/2026.5.4
• https://www.vulncheck.com/advisories/home-assistant-core-xss-via-shelly-media-player-py-thumb-uri

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