CVE-2026-34839
Summary
The Glances web server exposes a REST API (/api/4/*) that is accessible without authentication and allows cross-origin requests from any origin due to a permissive CORS policy (Access-Control-Allow-Origin: *).
This allows a malicious website to read sensitive system information from a running Glances instance in the victim’s browser, leading to cross-origin data exfiltration.
While a previous advisory exists for XML-RPC CORS issues, this report demonstrates that the REST API (/api/4/*) is also affected and exposes significantly more sensitive data.
Details
When Glances is started in web mode (e.g., glances -w -B 0.0.0.0), it exposes a REST API endpoint at:
http://<host>:61208/api/4/all
The server responds with:
Access-Control-Allow-Origin: *
This allows any origin to perform cross-origin requests and read responses.
The /api/4/all endpoint returns extensive system information, including:
- Process list (
processlist) - System details (hostname, OS, CPU info)
- Memory and disk usage
- Network interfaces and IP address
- Running services and metrics
Because no authentication is required by default, this data is accessible to any web page.
PoC
- Start Glances:
glances -w -B 0.0.0.0
- Create a malicious HTML file:
<!DOCTYPE html>
<html>
<body>
<script>
fetch("http://<victim-ip>:61208/api/4/all")
.then(r => r.json())
.then(data => {
console.log("DATA:", data);
});
</script>
</body>
</html>- Open the file in a browser while Glances is running.
- Observe that the browser successfully retrieves sensitive system information from the API.
This works cross-origin (e.g., from file:// or attacker-controlled domains).
Impact
A remote attacker can host a malicious website that, when visited by a victim running Glances, can:
- Read sensitive system information
- Enumerate running processes
- Identify network configuration and IP addresses
- Fingerprint the host system
This requires no authentication and no user interaction beyond visiting a web page. This represents a cross-origin information disclosure vulnerability and can aid further attacks such as reconnaissance or targeted exploitation.
Package Versions Affected
Automatically patch vulnerabilities without upgrading
CVSS Version
Related Resources
References
https://github.com/nicolargo/glances/security/advisories/GHSA-gfc2-9qmw-w7vh, https://nvd.nist.gov/vuln/detail/CVE-2026-34839, https://github.com/nicolargo/glances/commit/fdfb977b1d91b5e410bc06c4e19f8bedb0005ce9, https://github.com/nicolargo/glances