Eclipse Theia up to 1.72.x Browser Backend /services/shell-terminal missing origin validation in websockets

Summaryinfo

A vulnerability classified as critical has been found in Eclipse Theia up to 1.72.x. Impacted is an unknown function of the file /services/shell-terminal of the component Browser Backend. Performing a manipulation results in missing origin validation in websockets. This vulnerability is known as CVE-2026-10054. Remote exploitation of the attack is possible. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, was found in Eclipse Theia up to 1.72.x. This affects some unknown processing of the file /services/shell-terminal of the component Browser Backend. The manipulation with an unknown input leads to a missing origin validation in websockets vulnerability. CWE is classifying the issue as CWE-1385. The product uses a WebSocket, but it does not properly verify that the source of data or communication is valid. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-10054 since 05/29/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 1.73.0 eliminates this vulnerability.

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Productinfo

Vendor

• Eclipse

Name

• Theia

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19
• 1.20
• 1.21
• 1.22
• 1.23
• 1.24
• 1.25
• 1.26
• 1.27
• 1.28
• 1.29
• 1.30
• 1.31
• 1.32
• 1.33
• 1.34
• 1.35
• 1.36
• 1.37
• 1.38
• 1.39
• 1.40
• 1.41
• 1.42
• 1.43
• 1.44
• 1.45
• 1.46
• 1.47
• 1.48
• 1.49
• 1.50
• 1.51
• 1.52
• 1.53
• 1.54
• 1.55
• 1.56
• 1.57
• 1.58
• 1.59
• 1.60
• 1.61
• 1.62
• 1.63
• 1.64
• 1.65
• 1.66
• 1.67
• 1.68
• 1.69
• 1.70
• 1.71
• 1.72

License

• open-source

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