GHSA-GFC2-9QMW-W7VH
Vulnerability from github – Published: 2026-04-21 15:14 – Updated: 2026-05-04 20:08Summary
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://: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.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "Glances"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "4.5.4"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-34839"
],
"database_specific": {
"cwe_ids": [
"CWE-200",
"CWE-306",
"CWE-942"
],
"github_reviewed": true,
"github_reviewed_at": "2026-04-21T15:14:40Z",
"nvd_published_at": "2026-04-21T00:16:27Z",
"severity": "HIGH"
},
"details": "### Summary\nThe 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: *`).\n\nThis allows a malicious website to read sensitive system information from a running Glances instance in the victim\u2019s browser, leading to cross-origin data exfiltration.\n\nWhile 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.\n\n### Details\nWhen Glances is started in web mode (e.g., `glances -w -B 0.0.0.0`), it exposes a REST API endpoint at:\nhttp://\u003chost\u003e:61208/api/4/all\nThe server responds with:\nAccess-Control-Allow-Origin: *\n\nThis allows any origin to perform cross-origin requests and read responses.\n\nThe `/api/4/all` endpoint returns extensive system information, including:\n- Process list (`processlist`)\n- System details (hostname, OS, CPU info)\n- Memory and disk usage\n- Network interfaces and IP address\n- Running services and metrics\nBecause no authentication is required by default, this data is accessible to any web page.\n\n### PoC\n1. Start Glances:\nglances -w -B 0.0.0.0\n\n2. Create a malicious HTML file:\n\n```\n\u003c!DOCTYPE html\u003e\n\u003chtml\u003e\n\u003cbody\u003e\n\u003cscript\u003e\nfetch(\"http://\u003cvictim-ip\u003e:61208/api/4/all\")\n .then(r =\u003e r.json())\n .then(data =\u003e {\n console.log(\"DATA:\", data);\n });\n\u003c/script\u003e\n\u003c/body\u003e\n\u003c/html\u003e\n```\n2. Open the file in a browser while Glances is running.\n3. Observe that the browser successfully retrieves sensitive system information from the API.\nThis works cross-origin (e.g., from file:// or attacker-controlled domains).\n\n### Impact\nA remote attacker can host a malicious website that, when visited by a victim running Glances, can:\n\n- Read sensitive system information\n- Enumerate running processes\n- Identify network configuration and IP addresses\n- Fingerprint the host system\n\nThis 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.",
"id": "GHSA-gfc2-9qmw-w7vh",
"modified": "2026-05-04T20:08:23Z",
"published": "2026-04-21T15:14:40Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/nicolargo/glances/security/advisories/GHSA-gfc2-9qmw-w7vh"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34839"
},
{
"type": "WEB",
"url": "https://github.com/nicolargo/glances/commit/fdfb977b1d91b5e410bc06c4e19f8bedb0005ce9"
},
{
"type": "PACKAGE",
"url": "https://github.com/nicolargo/glances"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Glances: Cross-Origin Information Disclosure via Unauthenticated REST API (/api/4) due to Permissive CORS"
}
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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