{"id":"CVE-2026-34839","aliases":["GHSA-gfc2-9qmw-w7vh","PYSEC-2026-2175"],"url":"https://o3.security/vulnerability/CVE-2026-34839","summary":"Glances Vulnerable to 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://: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\n\n\n\n\n\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.","published":"2026-04-20T23:09:02.551Z","modified":"2026-08-12T03:51:44.808208888Z","cvss":null,"epss":{"score":0.00408,"percentile":0.33857,"asOf":"2026-08-14"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"glances","fixedVersion":"4.5.4"}],"fix":{"url":"https://github.com/nicolargo/glances/commit/fdfb977b1d91b5e410bc06c4e19f8bedb0005ce9","label":"nicolargo/glances@fdfb977"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34839.json"},{"type":"ADVISORY","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":"FIX","url":"https://github.com/nicolargo/glances/commit/fdfb977b1d91b5e410bc06c4e19f8bedb0005ce9"},{"type":"PACKAGE","url":"https://github.com/nicolargo/glances"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:44.808208888Z"}}