CVE-2026-34839: Glances: Cross-Origin Information Disclosure via Unauthenticated REST API (/api/4) due to Permissive CORS

CVE-2026-34839 · Severity: medium · CVSS 6.5 · Published 2026-04-21

Glances is an open-source system cross-platform monitoring tool. Prior to version 4.5.4, 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. Version 4.5.4 patches the issue.

Technologies: Nicolargo Glances, glances (PyPI). Vendors: Nicolargo, PyPI.

Quick answers

Is CVE-2026-34839 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-34839 being exploited in the wild.
How severe is CVE-2026-34839?
Medium severity, with a CVSS score of 6.5, published 21 April 2026.
Which products and versions are affected?
glances (PyPI) ECOSYSTEM:introduced=0,fixed=4.5.4.
Is there a fix for CVE-2026-34839?
Yes. glances (PyPI): upgrade to 4.5.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2026-34839?
Check whether you run Nicolargo Glances or glances (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • glances (PyPI): upgrade to 4.5.4 or later
    pip install "glances>=4.5.4"

Affected products

  • Nicolargo Glances
  • glances (PyPI) ECOSYSTEM:introduced=0,fixed=4.5.4

Identifiers

  • CVE-2026-34839
  • GHSA-gfc2-9qmw-w7vh
  • PYSEC-2026-2175

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