# CVE-2026-12609: Eclipse Theia - Path Traversal

> Live exploitation tracking for CVE-2026-12609 by the CrowdSec Live Exploit Tracker, built from real-world attack data crowdsourced from CrowdSec's global network.

Page: https://tracker.crowdsec.net/cves/CVE-2026-12609

## Key facts

- **Exploitation phase:** Limited Exploitation. The vulnerability is known but shows very limited attacker interest or exploitation activity.
- **CVSS score:** 7.5
- **Public exploit available:** Yes
- **Affected products:** Eclipse Foundation Eclipse Theia
- **Weaknesses:** CWE-22 (Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'))
- **Tags:** web_application

## 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.

## CrowdSec analysis

[CVE-2026-12609](https://euvd.enisa.europa.eu/vulnerability/CVE-2026-12609) is a high-severity path traversal vulnerability in Eclipse Theia versions 1.66.0 through 1.73.1. An unauthenticated network attacker can use encoded directory traversal sequences to escape a plugin’s directory and retrieve files readable by the Theia backend, potentially exposing sensitive information.

CrowdSec has been tracking this vulnerability and its exploits since 20th of October 2026.

CrowdSec has not observed any significant exploitation activity targeting CVE-2026-12609 across its network. As a result, no community-driven trend analysis is available for this vulnerability at this time.

Attackers target `/hostedPlugin/<pluginId>/` (the template uses the built-in `vscode_bat` plugin) with encoded path-traversal sequences to escape the plugin directory and read files accessible to the Eclipse Theia backend. The template probes for `/etc/passwd` to confirm successful unauthenticated file disclosure.

## Timeline

- 2026-08-05: CVE Published. CVE-2026-12609 is published to NVD.
- 2026-10-20: Rule Released. CrowdSec releases a rule to detect CVE-2026-12609 exploitation attempts against the CrowdSec Network.

## References

- https://gitlab.eclipse.org/security/vulnerability-reports/-/issues/524
- https://github.com/eclipse-theia/theia/security/advisories/GHSA-qmm6-p8q4-2g48
- https://gitlab.eclipse.org/security/cve-assignment/-/work_items/133
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-12609.yaml

## Live exploitation data

The [Live Exploit Tracker page](https://tracker.crowdsec.net/cves/CVE-2026-12609) follows observed exploitation activity for CVE-2026-12609. [Request an API key](https://tracker.crowdsec.net/request-api-key) for full access to its exploitation timeline, attacking IP addresses and blocklists.