Origin validation error in Eclipse Theia
Priority LOW 39CWE-942Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-346.
Summary
In Eclipse Theia 0.3.9 to 1.8.1, the "mini-browser" extension allows a user to preview HTML files in an iframe inside the IDE. But with the way it is made it is possible for a previewed HTML file to trigger an RCE. This exploit only happens if a user previews a malicious file..
Why it matters now
EPSS 0.00595 48th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed @theia/mini-browser (npm): 1.9.0
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Eclipse Foundation | Eclipse Theia | 0.3.9 and later; up to 1.8.1 | — | No fix listed | CNA |
| — | @theia/mini-browser (npm) | 0.3.9 to before 1.9.0 | 1.9.0 | Patch available | GHSA-v9w2-v7j9-rjpr |
- Eclipse Theia VendorEclipse Foundation Affected 0.3.9 and later; up to 1.8.1 Fixed in — No fix listed CNA
- @theia/mini-browser (npm) Vendor— Affected 0.3.9 to before 1.9.0 Fixed in 1.9.0 Patch available GHSA-v9w2-v7j9-rjpr
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:eclipse:theia:*:*:*:*:*:*:*:* | 0.3.9 – 1.8.1 | Vulnerable | Eclipse Foundation |
- cpe:2.3:a:eclipse:theia:*:*:*:*:*:*:*:* Versions 0.3.9 – 1.8.1 Vulnerable ·Eclipse Foundation
Remediation
- Fix · GHSA-v9w2-v7j9-rjpr @theia/mini-browser (npm) Fixed in 1.9.0 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2021-34435
- 2026-10-03 Alias added: GHSA-v9w2-v7j9-rjpr
References
More Eclipse Foundation Theia vulnerabilities
- TI-2026-12294 Prototype pollution in Eclipse Theia CVSS 4.0MEDIUM 5.7
- TI-2021-13470 Path traversal in Eclipse Theia CVSS 3.1CRITICAL 9.8
- TI-2020-16550 Cross-site scripting in Eclipse Theia CVSS 3.1CRITICAL 9.6
- TI-2026-10807 Path traversal in Eclipse Theia CVSS 3.1HIGH 7.5
- TI-2026-44283 Information disclosure in Eclipse Theia CVSS 3.1HIGH 7.5
- TI-2026-42788 Path traversal in Eclipse Theia CVSS 3.1HIGH 8.8
Sources
- CVE-2021-34435 · CVE Program
- CVE-2021-34435 · NVD
- FIRST EPSS
- GHSA-v9w2-v7j9-rjpr · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences