--- id: CVE-2026-34839 aliases: - GHSA-gfc2-9qmw-w7vh - PYSEC-2026-2175 title: >- Glances: Cross-Origin Information Disclosure via Unauthenticated REST API (/api/4) due to Permissive CORS summary: >- Glances: Cross-Origin Information Disclosure via Unauthenticated REST API (/api/4) due to Permissive CORS severity: medium cvss: 6.5 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N' vendor: glances product: glances ecosystem: pip affected: - glances < 4.5.4 patched: - glances 4.5.4 published: '2026-04-21' updated: '2026-07-13' source: OSV sourceUrl: 'https://osv.dev/vulnerability/GHSA-gfc2-9qmw-w7vh' references: - url: >- https://github.com/nicolargo/glances/security/advisories/GHSA-gfc2-9qmw-w7vh - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-34839' - url: >- https://github.com/nicolargo/glances/commit/fdfb977b1d91b5e410bc06c4e19f8bedb0005ce9 - url: 'https://github.com/nicolargo/glances' tags: - osv - pip epss: 0.00471 epssPercentile: 0.38117 ingestedAt: '2026-07-13T18:57:58.331Z' --- ## Overview ### 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://: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 1. Start Glances: glances -w -B 0.0.0.0 2. Create a malicious HTML file: ``` ``` 2. Open the file in a browser while Glances is running. 3. 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 packages - `glances < 4.5.4` ## Remediation Upgrade to a patched release: - `glances 4.5.4`