Eclipse Theia

Eclipse Theia <=1.69 Untrusted WS Git Exec Vulnerability
CVE-2026-19884 8.4 - High - August 14, 2026

In Eclipse Theia versions up to and including 1.69.0, opening a folder starts source control integration without requiring the user to trust the folder first. This affects applications built on Theia that include the git integration, such as the Theia IDE. Both Theia's own `@theia/git` extension and the builtin VS Code `git` extension run git commands such as `git status` as soon as a repository is detected. Since git honors repository-local configuration, a folder containing an attacker-controlled `.git/config` with `core.fsmonitor` (or a comparable hook-like setting) causes the configured command to be executed. The configuration can be delivered by burying a bare repository inside a regular repository (OVE-20210718-0001), so cloning an attacker-supplied repository and opening it in a Theia-based application is sufficient to execute arbitrary commands with the privileges of the user, without any confirmation prompt. As of 1.70.0, plugins that declare `capabilities.untrustedWorkspaces.supported: false`, which includes the builtin git extension, are no longer loaded or activated in an untrusted workspace, and the deprecated `@theia/git` extension has been removed, so no git command is executed against an untrusted folder.

Inclusion of Functionality from Untrusted Control Sphere

Eclipse Theia <=1.73.1 Unauth HTTP File Grab via @theia/filesystem
CVE-2026-61891 7.5 - High - August 05, 2026

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.

Directory traversal

Eclipse Theia <=1.73.1: Unauth File Write via @theia/fs POST /file-upload
CVE-2026-60009 8.8 - High - August 05, 2026

In Eclipse Theia versions up to and including 1.73.1, the `@theia/filesystem` backend binds `POST /file-upload` in every filesystem-enabled deployment. The handler takes an attacker-supplied absolute path from the multipart `uri` field and calls `fs.move(tmp, target, { overwrite: true })` with no workspace confinement and no authentication. 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. Because `multipart/form-data` is a CORS-safelisted request type, a cross-origin web page can trigger the write with no preflight and no credentials, resulting in an unauthenticated arbitrary file write outside the workspace to any absolute path the backend process can write. This can escalate to remote code execution, for example by overwriting a startup-executed file such as `~/.bashrc`. Electron mode uses a separate `ElectronSecurityToken` and is not affected via this path.

Session Riding

Eclipse Theia 1.66-1.73 Path Traversal via @theia/plugin-ext
CVE-2026-12609 7.5 - High - August 05, 2026

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.

Directory traversal

Prototype Pollution in Eclipse Theia PreferenceUtils.merge (0.7-1.73.1)
CVE-2026-14574 5.7 - Medium - August 05, 2026

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.

Prototype Pollution

Theia 1.26.0 - RPC /services/request-service Open Proxy via Server-side HTTP
CVE-2026-10055 8.5 - High - July 03, 2026

In Eclipse Theia since version 1.26.0, the backend /services/request-service RPC accepts an attacker-controlled URL from any client connected to the standard /services messaging endpoint, performs the HTTP request server-side, and returns the full response body to the caller. Because the destination URL is neither validated nor allowlisted, a remote attacker with access to the Theia service connection can issue server-side HTTP requests to localhost or other backend-reachable hosts and read their responses, exposing internal administrative endpoints, cloud instance metadata services, and other resources that are intentionally outside the browser network boundary. The vulnerability affects deployments where the Theia service connection is reachable by untrusted users (for example, multi-tenant or publicly-reachable Theia deployments).

SSRF

Eclipse Theia 1.8.1+ Terminal RPC WebSocket Auth Bypass
CVE-2026-10054 8.8 - High - July 03, 2026

In affected versions of Eclipse Theia (1.8.1 and later), the browser backend exposes privileged terminal RPC over WebSocket (/services/shell-terminal, /services/terminals/:id) without service-level authentication. WebSocket origin validation in @theia/core is fail-open: connections are accepted when the Origin header is missing or when no THEIA_HOSTS allowlist is configured (the default). The Socket.IO integration additionally replaces the real Origin header with a client-supplied fix-origin header that an attacker can control or omit. As a result, a foreign-origin web page visited by a user with a running Theia instance can open the /services WebSocket namespace, invoke terminal creation, attach to the resulting terminal data channel, execute arbitrary OS commands, and read their output. This affects both local developer setups (drive-by attack) and hosted or tunneled deployments without strong external authentication. A fix is in development that enforces same-origin validation by default, removes trust in the fix-origin header, gates HTTP and WebSocket access on a SameSite=Strict; HttpOnly connection-token cookie, and sanitizes shell terminal creation options.

1385

Eclipse Theia <1.69.0 Untrusted .theia/tasks.json Exec Risk
CVE-2026-44691 - June 18, 2026

In Eclipse Theia versions prior to 1.69.0, custom task definitions in workspace files (e.g. .theia/tasks.json, .vscode/tasks.json) could be executed without requiring workspace trust. An attacker could craft a malicious repository that, when cloned and opened in Theia, leads to execution of arbitrary commands with the user's privileges. In combination with AI chat features and a workspace .theia/settings.json that disabled tool confirmation, this could be triggered automatically by sending a message in the AI chat.

Inclusion of Functionality from Untrusted Control Sphere

Eclipse Theia <1.71.0 AI Chat Rendered Markdown Images Trigger External Requests
CVE-2026-22551 - June 18, 2026

In Eclipse Theia versions prior to 1.71.0, the AI chat rendered Markdown image tags from AI responses, triggering HTTP requests to arbitrary external URLs without restriction. Combined with prompt injection in a malicious workspace, an attacker could induce the AI agent to construct image URLs encoding sensitive information from the workspace or conversation context, exfiltrating it to attacker-controlled servers. The workspace trust enforcement introduced in v1.71.0 mitigates the documented attack chain by disabling AI features in untrusted workspaces.

Insertion of Sensitive Information Into Sent Data

Eclipse Theia <1.71.0 Indirect Prompt Injection via .prompts/*.prompttemplate
CVE-2026-46580 - June 18, 2026

In Eclipse Theia versions prior to 1.71.0, files matching the pattern .prompts/*.prompttemplate in a workspace were automatically loaded and could override or extend the AI agent's system prompts. An attacker could craft a malicious repository containing prompt template files that, when the workspace was opened in Theia, replaced the AI's system instructions with attacker-controlled content (indirect prompt injection). Combined with other AI chat features available in untrusted workspaces, this enabled attack chains leading to data exfiltration via Markdown image rendering or arbitrary command execution via task definitions.

Inclusion of Functionality from Untrusted Control Sphere

Eclipse Theia <=1.70.0 AI Chat Prompt Injection via File/Dir Names
CVE-2026-44688 - June 18, 2026

In Eclipse Theia versions prior to 1.71.0, the AI chat agent processed workspace file and directory names as part of its prompt context without distinguishing them from system instructions. An attacker could craft a malicious repository with adversarial directory or file names that, when analyzed by the AI agent, would cause the agent to follow attacker-controlled instructions (indirect prompt injection). Combined with other AI chat features available in untrusted workspaces, this enabled attack chains leading to data exfiltration via Markdown image rendering or arbitrary command execution via task definitions.

1427

In versions of the @theia/plugin-ext component of Eclipse Theia prior to 1.18.0, Webview contents can be hijacked
CVE-2021-41038 6.1 - Medium - November 10, 2021

In versions of the @theia/plugin-ext component of Eclipse Theia prior to 1.18.0, Webview contents can be hijacked via postMessage().

In Eclipse Theia 0.1.1 to 0.2.0, it is possible to exploit the default build to obtain remote code execution (and XXE)
CVE-2021-34436 9.8 - Critical - September 02, 2021

In Eclipse Theia 0.1.1 to 0.2.0, it is possible to exploit the default build to obtain remote code execution (and XXE) via the theia-xml-extension. This extension uses lsp4xml (recently renamed to LemMinX) in order to provide language support for XML. This is installed by default.

Directory traversal

In Eclipse Theia 0.3.9 to 1.8.1, the "mini-browser" extension allows a user to preview HTML files in an iframe inside the IDE
CVE-2021-34435 8.8 - High - September 01, 2021

In Eclipse Theia 0.3.9 to 1.8.1, the "mini-browser" extension allows a user to preview HTML files in an iframe inside the IDE. But with the way it is made it is possible for a previewed HTML file to trigger an RCE. This exploit only happens if a user previews a malicious file..

Origin Validation Error

In Eclipse Theia versions up to and including 0.16.0, in the notification messages there is no HTML escaping, so Javascript code
CVE-2021-28162 6.1 - Medium - March 12, 2021

In Eclipse Theia versions up to and including 0.16.0, in the notification messages there is no HTML escaping, so Javascript code can run.

Inclusion of Functionality from Untrusted Control Sphere

In Eclipse Theia versions up to and including 1.8.0, in the debug console there is no HTML escaping, so arbitrary Javascript code
CVE-2021-28161 6.1 - Medium - March 12, 2021

In Eclipse Theia versions up to and including 1.8.0, in the debug console there is no HTML escaping, so arbitrary Javascript code can be injected.

XSS

In Eclipse Theia versions up to and including 1.2.0, the Markdown Preview (@theia/preview)
CVE-2020-27224 9.6 - Critical - February 24, 2021

In Eclipse Theia versions up to and including 1.2.0, the Markdown Preview (@theia/preview), can be exploited to execute arbitrary code.

XSS

In Eclipse Theia versions 0.3.9 through 0.15.0
CVE-2019-17636 - March 10, 2020

In Eclipse Theia versions 0.3.9 through 0.15.0, one of the default pre-packaged Theia extensions is "Mini-Browser", published as "@theia/mini-browser" on npmjs.com. This extension, for its own needs, exposes a HTTP endpoint that allows to read the content of files on the host's filesystem, given their path, without restrictions on the requester's origin. This design is vulnerable to being exploited remotely through a DNS rebinding attack or a drive-by download of a carefully crafted exploit.

Insufficient Verification of Data Authenticity