Vulnerability Description
In Eclipse Theia versions 1.66.0 and up until including 1.73.1, the `@theia/plugin-ext` backend exposes the `/hostedPlugin/:pluginId/:path(*)` HTTP endpoint, which resolves the requested file path with `path.resolve(localPath, filePath)` without verifying that the resolved path stays within the plugin's directory. An unauthenticated network attacker can send percent-encoded `../` sequences (`%2e%2e%2f`) that decode into the path parameter and escape the plugin directory, allowing arbitrary files readable by the Theia backend process to be retrieved. Plugin IDs are derived deterministically from a plugin's publisher and name, so built-in plugins serve as reliable anchors that require no prior knowledge of the target system.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Eclipse | Theia | >= 1.66.0, < 1.74.0 |
Related Weaknesses (CWE)
References
- https://github.com/eclipse-theia/theia/security/advisories/GHSA-qmm6-p8q4-2g48Broken Link
- https://gitlab.eclipse.org/security/cve-assignment/-/work_items/133Vendor Advisory
- https://gitlab.eclipse.org/security/vulnerability-reports/-/issues/524Issue TrackingMitigationVendor Advisory
FAQ
What is CVE-2026-12609?
CVE-2026-12609 is a vulnerability with a CVSS score of 7.5 (HIGH). In Eclipse Theia versions 1.66.0 and up until including 1.73.1, the `@theia/plugin-ext` backend exposes the `/hostedPlugin/:pluginId/:path(*)` HTTP endpoint, which resolves the requested file path wit...
How severe is CVE-2026-12609?
CVE-2026-12609 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-12609?
Check the references section above for vendor advisories and patch information. Affected products include: Eclipse Theia.