PatchSiren cyber security CVE debrief
CVE-2026-10054 Eclipse Foundation CVE debrief
Eclipse Theia versions 1.8.1 and later have a vulnerability in the browser backend that exposes privileged terminal RPC over WebSocket without service-level authentication. This allows a foreign-origin web page to invoke terminal creation, execute arbitrary OS commands, and read their output. The vulnerability arises from fail-open WebSocket origin validation in @theia/core and the replacement of the real Origin header with a client-supplied fix-origin header by the Socket.IO integration.
- Vendor
- Eclipse Foundation
- Product
- Eclipse Theia
- CVSS
- HIGH 8.8
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-07-03
- Original CVE updated
- 2026-07-07
- Advisory published
- 2026-07-03
- Advisory updated
- 2026-07-07
Who should care
Users of Eclipse Theia, especially those with local developer setups or hosted deployments without strong external authentication, should be aware of this vulnerability and take necessary actions to mitigate it. This includes reviewing the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
Technical summary
The vulnerability arises from fail-open WebSocket origin validation in @theia/core and the replacement of the real Origin header with a client-supplied fix-origin header by the Socket.IO integration. This allows an attacker to control or omit the Origin header, enabling them to open the /services WebSocket namespace and execute arbitrary OS commands. 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.
Defensive priority
High priority should be given to patching or mitigating this vulnerability, especially in environments where strong external authentication is not in place.
Recommended defensive actions
- Apply the upcoming fix that enforces same-origin validation by default and removes trust in the fix-origin header.
- Gate HTTP and WebSocket access on a SameSite=Strict; HttpOnly connection-token cookie.
- Sanitize shell terminal creation options.
- Implement strong external authentication for deployments.
- Monitor for suspicious WebSocket connections and terminal activity.
- Review compensating controls for exposed systems while remediation is scheduled and verified.
- Track exceptions, retest remediated assets, and close the item only after evidence is documented.
Evidence notes
The CVE record was published on 2026-07-03T11:16:26.847Z and was last modified on 2026-07-07T05:16:48.237Z. The NVD entry is currently Deferred. There is limited information available about the specific details of the vulnerability and its impact. Defenders should verify the affected scope and vendor guidance.
Official resources
AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-03T11:16:26.847Z and has not been modified since then. The NVD entry is currently Deferred.