CVE-2023-41896
Fake websocket server installation permits full takeover in Home Assistant Core
Published Oct 19, 2023
CVSS 3.1 · 7.1 High
EPSS < 1%
KEV · Not listed
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.
Affected Products
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CVE record
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NVD configurations
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Red Hat packages
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OpenCVE enrichment
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Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||
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| home-assistant | core | affected |
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Configuration 1 [-]
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No data available yet.
Remediation
Tracking
Advisories
| Source | ID | Title |
|---|---|---|
 EUVD |
EUVD-2023-46375 | 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. |
Metrics
No CVSS v4.0
Attack Vector Network
Attack Complexity High
Privileges Required Low
Scope Unchanged
Confidentiality Impact High
Integrity Impact High
Availability Impact High
User Interaction Required
No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
Exploit prediction score: < 1% (0.315% probability within 30 days)
Key SSVC decision points have not yet been added.
References
History
No history.
Subscriptions
Weaknesses