Executive brief
Home Assistant includes an automatic discovery feature for IPP network printers using mDNS (Zeroconf). An attacker on the same local network can broadcast a fake printer announcement that tricks Home Assistant into making HTTP requests to internal services, such as databases or administrative panels, that are not normally accessible from the network. This could expose sensitive data or allow the attacker to interact with internal systems.
Technical details
The vulnerability is a Server-Side Request Forgery (SSRF) in the IPP Zeroconf integration (`homeassistant/components/ipp/config_flow.py`). When Home Assistant receives an mDNS announcement for `_ipp._tcp.local` services, it automatically extracts host, port, and path information without validation and makes an HTTP request to verify the printer. The HTTP client blindly follows 302 redirects, allowing an attacker to craft an mDNS response pointing to the attacker's server, which then redirects the request to internal addresses (127.0.0.1 or other localhost-bound services). No authentication or user interaction is required; the integration processes announcements automatically. The fix restricts cross-origin redirects from non-loopback hosts to loopback addresses, blocking DNS-based bypasses as well.
Affected products
- Home Assistant Home Assistant
Timeline
- 2026-09-22: disclosed
- other: CVE-2026-91129 assigned