Path Traversal in Eclipse Theia
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.
Vulnerability class: Path Traversal (Directory Traversal)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.016 (76.4th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 76th percentile — 76.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.016 · change: +0.011
Affected products
- Eclipse Theia
- Eclipse Foundation Theia — versions 1.66.0
Weakness classification (CWE)
References
- github.com/eclipse-theia/theia/security/advisories/GHSA-qmm6-p8q4-2g48 (Broken Link)
- gitlab.eclipse.org/security/cve-assignment/-/work_items/133 (Vendor Advisory)
- gitlab.eclipse.org/security/vulnerability-reports/-/issues/524 (Mitigation, Issue Tracking, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-12609?
- CVE-2026-12609 is a high-severity vulnerability in Eclipse Theia, classified under Path Traversal. CVSS score: 7.5/10. Published 2026-08-05.
- How severe is CVE-2026-12609?
- High severity. CVSS v3 base score is 7.5 out of 10.