CVE-2026-34839 Glances Vulnerable to Cross-Origin Information Disclosure via Unauthenticated REST API (/api/4) due to Permissive CORS
A malicious website can read sensitive system information from a running Glances instance via its unauthenticated REST API due to permissive CORS settings.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-34839?
CVE-2026-34839 is a high-severity vulnerability in nicolargo glances, published on 20 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-34839?
3 open source packages ship an affected version, including glances and Glances. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
glances PyPI | All versions | 4.5.4 |
glances PyPI | All versions | 4.5.4 |
Glances PyPI | All versions | 4.5.4 |
Products include Nicolargo Glances.
How do I fix CVE-2026-34839?
Upgrade glances to 4.5.4 or later.
Is CVE-2026-34839 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34839 exists.
Other vulnerabilities in nicolargo glances
- CVE-2026-32633 Glances's Browser API Exposes Reusable Downstream Credentials via `/api/4/serverslist`
- CVE-2026-32596 Glances exposes the REST API without authentication
- CVE-2026-30928 Glances Exposes Unauthenticated Configuration Secrets
- CVE-2026-32610 Glances's Default CORS Configuration Allows Cross-Origin Credential Theft
- CVE-2026-32634 Glances Central Browser Autodiscovery Leaks Reusable Credentials to Zeroconf-Spoofed Servers
Sources
Also known as DEBIAN-CVE-2026-34839, GHSA-gfc2-9qmw-w7vh, PYSEC-2026-2175, UBUNTU-CVE-2026-34839.