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Fencer Vulns
critical 9.6

CVE-2020-27224 json

Cross-site Scripting (XSS) in Eclipse Theia

published 2021-02-24 5 y ago modified 2026-06-17 4 mo ago also GHSA-gcm9-cc3r-c6vj , EUVD-2021-0825

cvss
9.6
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.6%
EPSS 2.6% chance of exploitation in 30 days, percentile 85%
public exploits
0
none known

Summary

In Eclipse Theia versions up to and including 1.2.0, the Markdown Preview (@theia/preview), can be exploited to execute arbitrary code.

Patch / fix

  • npm @theia/preview 1.3.0

Exploit prediction

2.59% chance of exploitation in the next 30 days, higher than 85% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/eclipse-theia/theia/issues/7954 referenced PoC, tagged "exploit" by a source, unverified
  • omespino.com https://omespino.com/write-up-google-bug-bounty-xss-to-cloud-shell-instance-takeover-rce-as-root-5000-usd/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 9.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
NVD 2.0 9.3 AV:N/AC:M/Au:N/C:C/I:C/A:C
GitHub 3.1 9.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
npm @theia/preview
<1.3.0
1.3.0

Affected products

  • The Eclipse Foundation Eclipse Theia

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.