CVE-2026-61891
Received Received - Intake

Path Traversal in Eclipse Theia IDE

Publication date: 2026-08-05

Last updated on: 2026-08-05

Assigner: Eclipse Foundation

Description
In Eclipse Theia versions up to and including 1.73.1, the `@theia/filesystem` backend exposes HTTP file-download endpoints (`GET /file`, `GET /files/`, `PUT /files/`) that convert a client-supplied URI directly to a filesystem path and stream the file, without confining it to the workspace or any allow-listed root. In browser (non-Electron) deployments the connection token is enforced only on WebSocket upgrades; the HTTP middleware in `@theia/core` re-issues the cookie and calls `next()` without rejecting tokenless HTTP requests, so these endpoints are reachable without a valid token. As a result an unauthenticated client can read any file readable by the backend process, including files outside the opened workspace (for example `/etc/hosts`, SSH keys, or tokens). Electron mode uses a separate `ElectronSecurityToken` and is not affected via this path.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published
2026-08-05
Last Modified
2026-08-05
Generated
2026-08-05
AI Q&A
2026-08-05
EPSS Evaluated
N/A
NVD
CVE-2026-61891
EUVD
EUVD-2026-53327

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
eclipse theia to 1.72.3 (inc)
eclipse theia *
eclipse theia to 1.73.1 (inc)

Helpful Resources

Exploitability

CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-36 The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize absolute path sequences such as "/abs/path" that can resolve to a location that is outside of that directory.
CWE-306 The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.
CWE-200 The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
CWE-22 The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

Attack-Flow Graph

AI Quick Actions

Instant insights powered by AI
Executive Summary

This vulnerability in Eclipse Theia versions up to 1.73.1 allows unauthenticated HTTP requests to access file-download endpoints that convert client-supplied URIs directly to filesystem paths. These endpoints stream files without restricting access to the workspace or allowed roots, enabling reading of any file readable by the backend process, including sensitive files outside the workspace.

Detection Guidance

Check if Theia is running and exposed to the network. Inspect HTTP requests to /file, /files/, or /files/ endpoints without authentication. Look for unauthorized file access attempts in logs.

Impact Analysis

An attacker could exploit this to read sensitive files on the server, such as configuration files, SSH keys, or tokens. This could lead to unauthorized access, data leaks, or further attacks if credentials or keys are exposed.

Compliance Impact

This vulnerability could violate compliance requirements by exposing sensitive data, such as personal or health information, to unauthorized parties. GDPR and HIPAA mandate strict data protection, and such a breach could result in legal penalties or loss of trust.

Mitigation Strategies

Upgrade Theia to a version beyond 1.73.1. Restrict network access to Theia instances. Disable unauthenticated HTTP endpoints if possible. Use Electron mode for additional security.

Chat Assistant

Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-61891. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70

EPSS Chart