CVE-2026-64823 home-assistant CVE debrief

Who should care

Users of Home Assistant Core before version 2026.5.4 who have the Shelly integration configured should be aware of this vulnerability and take steps to mitigate it. This includes operators, platform administrators, vulnerability management teams, and security teams responsible for ensuring the security and integrity of their Home Assistant Core deployments.

Technical summary

The vulnerability exists in the Shelly integration's async_get_media_image() method in Home Assistant Core before version 2026.5.4. Attackers controlling a Shelly device's thumb field can serve arbitrary HTML content by supplying a data URI with a text/html content type without validation against an image-only allowlist. This allows attackers to 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.

Defensive priority

Low

Recommended defensive actions

• Update Home Assistant Core to version 2026.5.4 or later
• Restrict access to the Shelly integration's async_get_media_image() method
• Monitor for suspicious activity in the Home Assistant web origin
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record was published on 2026-07-21T16:17:21.230Z and was last modified on 2026-07-22T15:17:21.770Z. The NVD entry is currently Deferred. Evidence is limited to CVE and NVD information. Defenders should verify affected scope and vendor guidance with official sources.

Official resources