CVE-2026-61891 Path traversal in Eclipse Theia
Unauthenticated attackers can read arbitrary files on the server via path traversal in Eclipse Theia's HTTP file endpoints due to missing token validation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-61891?
CVE-2026-61891 is a high-severity path traversal vulnerability in Eclipse Theia, published on 5 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-61891?
It affects 1 product.
Products include Eclipse Theia.
How do I fix CVE-2026-61891?
No fix has been published for CVE-2026-61891 yet. Limit exposure of the affected software until one is available.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-61891 being exploited?
There is no known exploitation of CVE-2026-61891 in the wild and no public exploit code.
Other vulnerabilities in Eclipse Theia
- CVE-2021-34436 XML external entity in Eclipse Theia
- CVE-2020-27224 Cross-site Scripting (XSS) in Eclipse Theia
- CVE-2026-60009 File upload in Eclipse Theia
- CVE-2021-34435 Remote code execution in Eclipse Theia
- CVE-2026-44688 [Eclipse Theia] Indirect Prompt Injection via Adversarial Workspace File and Directory Names in AI Chat
Sources
Also known as GHSA-qqc8-9538-25v4, GHSA-xrrm-6636-87r2.