CVE-2026-34839: Glances Cross-Origin Information Disclosure Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gfc2-9qmw-w7vh",
  "modified" : "2026-05-04T20:08:23Z",
  "published" : "2026-04-21T15:14:40Z",
  "aliases" : [ "CVE-2026-34839" ],
  "summary" : "Glances: Cross-Origin Information Disclosure via Unauthenticated REST API (/api/4) due to Permissive CORS",
  "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’s 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://<host>: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<!DOCTYPE html>\n<html>\n<body>\n<script>\nfetch(\"http://<victim-ip>:61208/api/4/all\")\n  .then(r => r.json())\n  .then(data => {\n    console.log(\"DATA:\", data);\n  });\n</script>\n</body>\n</html>\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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N"
  }, {
    "type" : "CVSS_V4",
    "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "Glances"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.5.4"
      } ]
    } ]
  } ],
  "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"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-200", "CWE-306", "CWE-942" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-21T15:14:40Z",
    "nvd_published_at" : "2026-04-21T00:16:27Z"
  }
}