CVE-2023-41896 Fake websocket server installation permits full takeover in Home Assistant Core
Attackers can force WebSocket connections to malicious servers via crafted links, enabling XSS and full account takeover in Home Assistant.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2023-41896?
CVE-2023-41896 is a high-severity cross-site scripting vulnerability in home-assistant core, published on 19 Oct 2023. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Home assistant is an open source home automation. Whilst auditing the frontend code to identify hidden parameters, Cure53 detected `auth_callback=1`, which is leveraged by the WebSocket authentication logic in tandem with the `state` parameter. The state parameter contains the `hassUrl`, which is subsequently utilized to establish a WebSocket connection. This behavior permits an attacker to create a malicious Home Assistant link with a modified state parameter that forces the frontend to connect to an alternative WebSocket backend. Henceforth, the attacker can spoof any WebSocket responses and trigger cross site scripting (XSS). Since the XSS is executed on the actual Home Assistant frontend domain, it can connect to the real Home Assistant backend, which essentially represents a comprehensive takeover scenario. Permitting the site to be iframed by other origins, as discussed in GHSA-935v-rmg9-44mw, renders this exploit substantially covert since a malicious website can obfuscate the compromise strategy in the background. However, even without this, the attacker can still send the `auth_callback` link directly to the victim user. To mitigate this issue, Cure53 advises modifying the WebSocket code’s authentication flow. An optimal implementation in this regard would not trust the `hassUrl` passed in by a GET parameter. Cure53 must stipulate the significant time required of the Cure53 consultants to identify an XSS vector, despite holding full control over the WebSocket responses. In many areas, data from the WebSocket was properly sanitized, which hinders post-exploitation. The audit team eventually detected the `js_url` for custom panels, though generally, the frontend exhibited reasonable security hardening. This issue has been addressed in Home Assistant Core version 2023.8.0 and in the npm package home-assistant-js-websocket in version 8.2.0. Users are advised to upgrade. There are no known workarounds for this vulnerability.
Weakness: CWE-345
Which versions are affected by CVE-2023-41896?
It affects 2 products.
Products include Home-Assistant Home-Assistant, Home-Assistant Home-Assistant-Js-Websocket.
How do I fix CVE-2023-41896?
No fix has been published for CVE-2023-41896 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-2023-41896 being exploited?
There is no known exploitation of CVE-2023-41896 in the wild and no public exploit code.
Other vulnerabilities in home-assistant core
- CVE-2023-27482 Auth bypass in core
- CVE-2023-41895 Cross-site Scripting via auth_callback login in Home Assistant Core
- CVE-2023-41897 Lack of XFO header allows clickjacking in Home Assistant Core
- CVE-2026-54317 Home Assistant: Konnected alarm-panel switch state and zone topology disclosed to unauthenticated actors on the LAN
- CVE-2020-36517 Information disclosure in n/a