CVE-2026-14574

In Eclipse Theia versions 0.7.0 and up until including 1.73.1, the `PreferenceUtils.merge` function in `@theia/core` recursively merges preference values without rejecting prototype-related keys (`__proto__`, `constructor`, `prototype`). Because this function is invoked by `PreferenceServiceImpl.doResolve` for every preference resolution across scopes (default, user, workspace, folder), a crafted preference value in a workspace settings file (`.theia/settings.json` or `.vscode/settings.json`) can pollute `Object.prototype` when the user opens the workspace, potentially altering application logic across the Theia process.

• https://github.com/eclipse-theia/theia/security/advisories/GHSA-f3w9-qfw3-xr32 Broken Link
• https://gitlab.eclipse.org/security/vulnerability-reports/-/issues/567 Exploit, Mitigation, Vendor Advisory, Issue Tracking
• https://gitlab.eclipse.org/security/vulnerability-reports/-/work_items/567 Exploit, Mitigation, Vendor Advisory

• https://github.com/eclipse-theia/theia/security/advisories/GHSA-f3w9-qfw3-xr32 Broken Link
• https://gitlab.eclipse.org/security/cve-assignment/-/work_items/157 Vendor Advisory
• https://gitlab.eclipse.org/security/vulnerability-reports/-/issues/567 Exploit, Mitigation, Vendor Advisory, Issue Tracking
• https://gitlab.eclipse.org/security/vulnerability-reports/-/work_items/567 Exploit, Mitigation, Vendor Advisory