What’s Vulnerable › Vulnerabilities

CVE-2026-12609

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.6% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-08-05 · updated 2026-10-23
• Weakness: CWE-22

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.

Affected products

• Eclipse Foundation Eclipse Theia: from 1.66.0 before 1.74.0 — fixed in 1.74.0

How to fix

Upgrade to a fixed version: Eclipse Foundation Eclipse Theia 1.74.0. Check the vendor advisory for mitigations.

References

• https://github.com/eclipse-theia/theia/security/advisories/GHSA-qmm6-p8q4-2g48
• https://gitlab.eclipse.org/security/cve-assignment/-/work_items/133
• https://gitlab.eclipse.org/security/vulnerability-reports/-/issues/524

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