CVE-2021-34436Network attack vector

Remote code execution via traversed DTD cache path

Published Sep 2, 2021 · Updated Aug 4, 2024

XXE in Eclipse Theia 0.1.1 through 0.2.0 allows attackers to execute code through the default XML extension and malicious XML. The bundled outdated lsp4xml server retrieves an external DTD and accepts traversal segments in its cache path, writing the DTD outside ~/.lsp4xml/cache/. The attack requires Theia to open attacker-controlled XML, after which files can be written into the service user's home directory and executed.

CVSS severity9.8
Critical
EPSS probability2.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

XXE in Eclipse Theia 0.1.1 through 0.2.0 allows attackers to execute code through the default XML extension and malicious XML. The bundled outdated lsp4xml server retrieves an external DTD and accepts traversal segments in its cache path, writing the DTD outside ~/.lsp4xml/cache/. The attack requires Theia to open attacker-controlled XML, after which files can be written into the service user's home directory and executed.

The record

CVE
CVE-2021-34436
Published
Sep 2, 2021
Updated
Aug 4, 2024
Vendor
The Eclipse Foundation
Product
Eclipse Theia
Classifications
CWE-22, CWE-611, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 2, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.1.1
  2. Affected versionversion=0.1.2
  3. Affected versionversion=0.2.0-next.28bc2735
  4. Affected versionversion=0.2.0-next.41406d98
  5. Affected versionversion=0.2.0-next.a2958907

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Eclipse Foundation · Eclipse Theiaversion=0.1.1; version=0.1.2; version=0.2.0-next.28bc2735; version=0.2.0-next.41406d98; version=0.2.0-next.a2958907

Published CVSS scores

7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CWE-611Improper Restriction of XML External Entity Reference
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo