CVE-2021-34435

Name: CVE-2021-34435
Creator: NVD / NIST
Published: 2021-09-01T18:15:09.107+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 0.60%

Last modified Jun 17, 2026

CVE-2021-34435 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. 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. EPSS estimates a 0.60% chance of exploitation in the next 30 days.

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..

Metrics

CVSS 3.1

8.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS Probability

0.60%

43.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Eclipse	Theia	>= 0.3.9, <= 1.8.1

References

https://bugs.eclipse.org/bugs/show_bug.cgi?id=568018Exploit, Patch, Vendor Advisory
https://bugs.eclipse.org/bugs/show_bug.cgi?id=568018Exploit, Patch, Vendor Advisory

Timeline

Published: Sep 1, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-34435?

How severe is CVE-2021-34435?

CVE-2021-34435 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 0.60% probability of exploitation in the next 30 days.

How do I fix CVE-2021-34435?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-34435?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST