# 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.

- **Severity:** Low 2.1 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N`)
- **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 available:** No
- **Published:** 21 Jul 2026
- **Updated:** 22 Jul 2026
- **Also known as:** GHSA-r3v5-j696-5grq

## 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 (Improper Neutralization of Input During Web Page Generation)

## 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.

## Is CVE-2026-64823 being exploited?

There is no known exploitation of CVE-2026-64823 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64823 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-64823 in the wild and no public exploit code.

Affected product: home-assistant Home Assistant Core. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-64823/ (Markdown: https://insights.sbomify.com/CVE-2026-64823/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64823
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64823
- OSV: https://osv.dev/vulnerability/CVE-2026-64823

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64823/
Summaries are generated and may contain mistakes; the official description above is the record.