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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

7.1 · 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 · score source

EPSS

• CVE-2026-34839: 0.41% estimated exploitation activity in the next 30 days; percentile 35.11 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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://<host: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…

Published by the source

21 Apr 2026, 15:14 UTC

Last modified by the source

13 Jul 2026, 07:26 UTC

Source last checked

26 Oct 2026, 13:40 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-gfc2-9qmw-w7vh

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-gfc2-9qmw-w7vh

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# Patch Next advisory brief: CVE-2026-34839

Advisory: Glances: Cross-Origin Information Disclosure via Unauthenticated REST API (/api/4) due to Permissive CORS
IDs: CVE-2026-34839, GHSA-gfc2-9qmw-w7vh
Record: https://patchnext.com/advisories/cve-2026-34839 (revision 3, source checked 26 Oct 2026, 13:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: glances 4.5.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI glances: affected < 4.5.4; fixed in 4.5.4

## Suggested inspection (read-only)
- `python -m pip show glances`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on glances.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-gfc2-9qmw-w7vh (OSV record GHSA-gfc2-9qmw-w7vh lists affected ranges: PyPI glances >=0 <4.5.4 (fixed))
- Verified: https://github.com/advisories/GHSA-gfc2-9qmw-w7vh (GitHub-reviewed advisory GHSA-gfc2-9qmw-w7vh lists affected ranges: PyPI glances >=0 <4.5.4)

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