CVE-2026-46611

Glances: XML-RPC Server Missing Host Header Validation Enables DNS Rebinding Attack

Published

2026-06-22

Modified

2026-07-21

EPSS percentile

5%

Aliases

GHSA-w856-8p3r-p338

Sources

github-advisory

Summary

### 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 ' getAllPlugins<

Affected packages

Remediation: Upgrade to 4.5.5 or later.

References

• https://github.com/advisories/GHSA-w856-8p3r-p338