CVE-2026-10054 Missing authorization in Eclipse Theia
Attackers can execute arbitrary OS commands via unauthenticated WebSocket terminal access in Eclipse Theia due to missing origin validation and authentication.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-10054?
CVE-2026-10054 is a high-severity missing authorization vulnerability in Eclipse Theia, published on 3 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
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.
Which versions are affected by CVE-2026-10054?
How do I fix CVE-2026-10054?
No fix has been published for CVE-2026-10054 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-10054 being exploited?
There is no known exploitation of CVE-2026-10054 in the wild and no public exploit code.
Sources
Also known as GHSA-78g8-vm3p-97c6.