CVE-2026-12609

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.

• CWE-22

• 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 Tracking, Mitigation, Vendor Advisory

Published

Aug 5, 2026

Last Modified

Oct 23, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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