CVE-2026-64823 Home Assistant Core < 2026.5.4 XSS via Shelly media_player.py thumb URI
Attackers can execute arbitrary scripts in Home Assistant via malicious Shelly device data, leading to session token theft and unauthorized control of smart home devices.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-64823?
CVE-2026-64823 is a low-severity cross-site scripting vulnerability in home-assistant Home Assistant Core, published on 21 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-64823?
How do I fix CVE-2026-64823?
No fix has been published for CVE-2026-64823 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-64823 being exploited?
There is no known exploitation of CVE-2026-64823 in the wild and no public exploit code.
Sources
Also known as GHSA-r3v5-j696-5grq.