CVE-2021-34436

Name: CVE-2021-34436
Creator: NVD / NIST
Published: 2021-09-02T21:15:07.977+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 2.15%

Last modified Jun 17, 2026

CVE-2021-34436 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. In Eclipse Theia 0.1.1 to 0.2.0, it is possible to exploit the default build to obtain remote code execution (and XXE) via the theia-xml-extension. This extension uses lsp4xml (recently renamed to LemMinX) in order to provide language support for XML. EPSS estimates a 2.15% chance of exploitation in the next 30 days.

Description

In Eclipse Theia 0.1.1 to 0.2.0, it is possible to exploit the default build to obtain remote code execution (and XXE) via the theia-xml-extension. This extension uses lsp4xml (recently renamed to LemMinX) in order to provide language support for XML. This is installed by default.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

2.15%

79.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Eclipse	Theia	>= 0.1.1, <= 0.2.0

References

https://bugs.eclipse.org/bugs/show_bug.cgi?id=563174Vendor Advisory
https://bugs.eclipse.org/bugs/show_bug.cgi?id=563174Vendor Advisory

Timeline

Published: Sep 2, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-34436?

How severe is CVE-2021-34436?

CVE-2021-34436 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 2.15% probability of exploitation in the next 30 days.

How do I fix CVE-2021-34436?

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-2021-34436?

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

Scan your code now

Source: NVD / NIST