CVE-2026-10054
HIGHDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 6% of all known CVEs.
References
Related Vulnerabilities
Other CWE-306 (Missing Authentication for Critical Function) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-3248 | Critical | 9.8 | 100% | KEV + Ransom | Fix |
| CVE-2017-10271 | High | 7.5 | 100% | KEV + Ransom | - |
| CVE-2023-42793 | Critical | 9.8 | 100% | KEV + Ransom | Fix |
| CVE-2022-1388 | Critical | 9.8 | 100% | KEV + Ransom | Fix |
| CVE-2026-33017 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2021-37415 | Critical | 9.8 | 100% | KEV | - |
Common questions
How do I fix CVE-2026-10054?
No published fix for CVE-2026-10054 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-10054 being actively exploited?
Not that we know of. CVE-2026-10054 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.16% is the estimated probability that it will be exploited in the next 30 days. That is higher than 6% of all scored CVEs.
How severe is CVE-2026-10054?
CVE-2026-10054 has a CVSS v3 base score of 8.8, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-07.