CVE-2026-3990Public exploitNetwork attack vector

Reflected XSS via unsanitized Sandcastle URL data

Published Mar 12, 2026 · Updated Mar 12, 2026

Cross-site scripting in CesiumJS 1.137.0 allows remote attackers to execute JavaScript via a crafted Sandcastle demo URL. The standalone.html demo decodes the c URL-fragment value, decompresses and parses its JSON, then assigns code, html, and baseHref to innerHTML sinks without sanitization. Exploitation requires a victim to open the crafted link, and Cesium disputes applicability because Sandcastle is repository demo code outside the CesiumJS library product.

CVSS severity4.3
Medium
EPSS probability0.26%
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

Cross-site scripting in CesiumJS 1.137.0 allows remote attackers to execute JavaScript via a crafted Sandcastle demo URL. The standalone.html demo decodes the c URL-fragment value, decompresses and parses its JSON, then assigns code, html, and baseHref to innerHTML sinks without sanitization. Exploitation requires a victim to open the crafted link, and Cesium disputes applicability because Sandcastle is repository demo code outside the CesiumJS library product.

The record

CVE
CVE-2026-3990
Published
Mar 12, 2026
Updated
Mar 12, 2026
Vendor
Cesium
Product
CesiumJS
Classifications
CWE-94, CWE-79, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 12, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 12, 2026Record 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=1.137

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Cesium · CesiumJSversion=1.137

Published CVSS scores

5.0VulDBAV:N/AC:L/Au:N/C:N/I:P/A:N
4.3VulDBCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
2.1VulDBCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1204.001Malicious Link

Public exploit references

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