Is CVE-2026-3990 actively exploited?

No active exploitation of CVE-2026-3990 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-3990 be exploited remotely?

Yes. CVE-2026-3990 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-3990?

CVE-2026-3990 has a CVSS score of 4.3 (MEDIUM).

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MEDIUM

CVE-2026-3990

CWE-79Published: March 12, 2026· Updated: Mar 12, 2026

4.3

CVSS v3.1

EPSS:0.03%probability of exploitation in 30 daysPercentile:8.4th

Official Description

A security flaw has been discovered in CesiumGS CesiumJS up to 1.137.0. Affected by this issue is some unknown functionality of the file Apps/Sandcastle/standalone.html. The manipulation of the argument c results in cross site scripting. The attack can be launched remotely. The exploit has been released to the public and may be used for attacks. The presence of this vulnerability remains uncertain at this time. The vendor was contacted early about this disclosure but did not respond in any way. According to CVE-2023-48094, "the vendor's position is that Apps/Sandcastle/standalone.html is part of the CesiumGS/cesium GitHub repository, but is demo code that is not part of the CesiumJS JavaScript library product."

NVD Source

Technical Analysis

CVE-2026-3990 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.

From a weakness classification perspective (CWE-79): Cross-site scripting (XSS) vulnerabilities allow attackers to inject malicious scripts into web pages viewed by other users.