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HIGH severity

Remote code execution in Eclipse TheiaGHSA-v9w2-v7j9-rjpr

HIGHFix: eclipse-theia/theia#8759

GHSA-v9w2-v7j9-rjpr is a high-severity (CVSS 8.8) CWE-942 vulnerability in @theia/mini-browser. 1 public exploit reference exists, so weaponization risk is real. A fix is available for @theia/mini-browser — see the affected versions and patch details below.

Also known asCVE-2021-34435
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs47th percentile — riskier than 47% of all scored CVEsHighest risk
0.00%0.37%0.73%1.10%0.1%0.1%0.6%0.6%0.6%May 26Jul 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-v9w2-v7j9-rjpr by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

9other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
@theia/mini-browsernpm
11Kdownloads / week

Description

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..

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npm@theia/mini-browser≥ 0.3.9&&< 1.9.01.9.0npm install @theia/mini-browser@1.9.0

Affected Products

1 product · 1 configurations
Application
theiaeclipse
≥ 0.3.9 && ≤ 1.8.1
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

In Eclipse Theia 0.3.9 to 1.8.1, the "mini-browser" extension allows a u…

bugs.eclipse.orgNVDSep 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @theia/mini-browser, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update @theia/mini-browser to 1.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-v9w2-v7j9-rjpr is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

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Remote code execution in Eclipse Theia (High 8.8)