# Remediation Handoff: CVE-2026-12609

## Summary

NVD: 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... NVD: 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. NVD: 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.

## Why it matters

CVSS severity is HIGH with score 7.5. EPSS percentile is 0.3374. KEV status is not listed in KEV. Use this as a defensive priority handoff, not as an execution instruction.

## Affected context

* Vendor: eclipse
* Product: theia
* Component: unknown
* Version / CPE / PURL: unknown

## Remediation context

* Recommended route: vendor_patch_or_mitigation
* Vendor/advisory reference: official_reference_present
* Patch status: requires_confirmation
* Fixed version: unknown
* 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

## Human checklist

* Confirm whether the listed product or package is present.
* Confirm affected version.
* Review vendor advisory or official source.
* Confirm patch, fixed version, mitigation, workaround, or monitor-only decision.
* Confirm exposure.
* Document remediation status.

## Safe AI / Codex handoff

* Goal: Prepare a defensive remediation plan for CVE-2026-12609 using only provided public-safe source context and any separate repo context supplied by the user.
* Allowed actions: summarize vendor guidance, prepare a defensive remediation plan, identify affected dependencies only when repo context is separately provided by the user, suggest tests and validation steps, document human verification questions
* Disallowed actions: generate offensive code, provide payloads, scan external targets, change production systems, merge or deploy changes, create GitHub issues or pull requests without explicit separate approval
* Acceptance criteria: Affected product or dependency presence is confirmed by a human., Affected version is confirmed or marked not applicable., Official advisory or source reference is reviewed., Patch, fixed version, mitigation, workaround, or monitor-only decision is documented., Validation steps are proposed without external scanning or production mutation.
* Human approval required: true

## Safety note

This handoff is for defensive triage and remediation planning only. It excludes offensive procedure, payload material, external target scan guidance, and auto-remediation.