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CVE-2026-64823 home-assistant CVE debrief

CVE-2026-64823 is a cross-site scripting vulnerability in Home Assistant Core before version 2026.5.4. The vulnerability exists in the Shelly integration's async_get_media_image() method, which 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. This vulnerability enables attackers to cause the media player proxy endpoint to serve attacker-controlled bytes with Content-Type text/html in the Home Assistant web origin, potentially leading to theft of session tokens from local storage and authenticated calls to sensitive service endpoints including lock, alarm, and cover controls.

Vendor
home-assistant
Product
Home Assistant Core
CVSS
LOW 2.1
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-21
Original CVE updated
2026-07-22
Advisory published
2026-07-21
Advisory updated
2026-07-22

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.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-64823 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-64823

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-64823 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-64823

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.