Eclipse Theia up to 1.73.1 HTTP Endpoint path.resolve path path traversal

Summaryinfo

A vulnerability categorized as problematic has been discovered in Eclipse Theia up to 1.73.1. This issue affects the function path.resolve of the component HTTP Endpoint. Executing a manipulation of the argument path can lead to path traversal. This vulnerability is registered as CVE-2026-12609. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability was found in Eclipse Theia up to 1.73.1. It has been declared as problematic. This vulnerability affects the function path.resolve of the component HTTP Endpoint. The manipulation of the argument path with an unknown input leads to a path traversal vulnerability. The CWE definition for the vulnerability is CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. As an impact it is known to affect confidentiality. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability was named CVE-2026-12609 since 06/18/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1006 by the MITRE ATT&CK project.

Upgrading to version 1.74.0 eliminates this vulnerability.

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Productinfo

Vendor

• Eclipse

Name

• Theia

Version

• 1.73.0
• 1.73.1

License

• open-source

CPE 2.3info

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CPE 2.2info

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