Vulnerability · Published Jul 21, 2026 · Assigned by VulnCheck

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

Medium 4.7

In plain English

A medium-severity cross-site scripting in Home Assistant Core from home-assistant. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities).

Severity (CVSS 3.1)4.7Medium

Exploit odds (30 days)0.3%top 77.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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.

Affected products (as reported)

Vendor	Product	Versions
home-assistant	Home Assistant Core	0 – before 2026.5.4

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N

References

Release Notes release-notes
Pull Request issue-tracking
Patch Commit patch
https://www.vulncheck.com/advisories/home-assistant-core-xss-via-shelly-media-player-py-thumb-uri third-party-advisory