CVE-2026-55566: Yamcs core Cross-Site Scripting Vulnerability
MODERATECVE-2026-55566 is a MODERATE (CVSS 4.3) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Yamcs core libraries in the Maven ecosystem. The issue involves yamcs has dom xss in extension routing. Remediation is available by upgrading affected packages to version 5.13.2, 5.12.8.
CVE-2026-55566 at a Glance
Security Impact
CVSS: 4.3
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N).
How to Fix CVE-2026-55566
To remediate this vulnerability, upgrade all affected Yamcs core dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
<dependency>
<groupId>org.yamcs</groupId>
<artifactId>yamcs-core</artifactId>
<version>5.13.2</version>
</dependency><dependency>
<groupId>org.yamcs</groupId>
<artifactId>yamcs-core</artifactId>
<version>5.12.8</version>
</dependency>Run the following command in your project directory to verify that all resolved dependencies use the patched release:
mvn dependency:tree -Dincludes=org.yamcsHow to Check if You Are Affected
To determine whether your Java application is affected by CVE-2026-55566, inspect your build dependencies using the Maven Dependency Plugin:
mvn dependency:tree -Dincludes=org.yamcsAnalyze the terminal output to locate any version of Yamcs core in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.13.2), your application is affected.
Note: The mvn dependency:tree -Dincludes=org.yamcs command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In Yamcs core, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-55566 Affected Yamcs core Versions
2 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
org.yamcs:yamcs-core
|
Maven |
≥ 5.13.0
< 5.13.2
|
5.13.2
|
|
org.yamcs:yamcs-core
|
Maven |
< 5.12.8
|
5.12.8
|
References
Frequently Asked Questions
What is CVE-2026-55566?
Which Yamcs core versions are affected?
What version fixes CVE-2026-55566?
Is yamcs-core affected?
What is the CVSS score of CVE-2026-55566?
What CWE is associated with CVE-2026-55566?
How can I check Maven dependencies for CVE-2026-55566?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-9272-wg2r-7xmx",
"modified" : "2026-08-28T17:32:16Z",
"published" : "2026-08-28T17:32:16Z",
"aliases" : [ "CVE-2026-55566" ],
"summary" : "Yamcs has DOM XSS in Extension Routing",
"details" : "**Attack type**: Unauthenticated remote \n**Impact**: Execution of arbitrary JavaScript in a user’s browser.\n**Affected components**: extension.matcher.ts:12, extension.component.ts:40, app.component.ts:134.\n\nYamcs is vulnerable to cross-site scripting in the /ext URL endpoint. By inputting specially crafted code into the URL, an attacker can execute arbitrary JavaScript code in a user’s browser. This URL may be sent to a user via a phishing email.\n \n<img width=\"940\" height=\"294\" alt=\"image\" src=\"https://github.com/user-attachments/assets/d886d65c-9bb5-4599-ac11-55db83aafc0e\" />\n\nSteps to Reproduce:\n1.\tStart a Yamcs instance.\n2.\tInsert the following URL into the browser and press enter (change ‘myproject’ to the name of your instance):\n```\nhttp://localhost:8090/ext/img%20src%3Dx%20onerror%3Dalert%281%29?c=myproject\n```\n3.\tYou will receive an alert with the number ‘1’ in it.\n\nRecommendations:\n1.\tUse document.createElement instead of innerHTML in extension.component.ts.\n2.\tValidate the extension against registered plugin IDs.\n3.\tEnforce a strict custom-element-name regex before mounting.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Maven",
"name" : "org.yamcs:yamcs-core"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "5.13.0"
}, {
"fixed" : "5.13.2"
} ]
} ],
"database_specific" : {
"last_known_affected_version_range" : "<= 5.13.1"
}
}, {
"package" : {
"ecosystem" : "Maven",
"name" : "org.yamcs:yamcs-core"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "5.12.8"
} ]
} ],
"database_specific" : {
"last_known_affected_version_range" : "<= 5.12.7"
}
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/yamcs/yamcs/security/advisories/GHSA-9272-wg2r-7xmx"
}, {
"type" : "WEB",
"url" : "https://github.com/yamcs/yamcs/commit/8e18e279d8ce761c21f4f67bbd06a1bff804d297"
}, {
"type" : "WEB",
"url" : "https://github.com/yamcs/yamcs/commit/ecf34a4e2ccbe085e6ceff0253595b24d5ecb4aa"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/yamcs/yamcs"
}, {
"type" : "WEB",
"url" : "https://github.com/yamcs/yamcs/releases/tag/yamcs-5.12.8"
}, {
"type" : "WEB",
"url" : "https://github.com/yamcs/yamcs/releases/tag/yamcs-5.13.2"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-79" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2026-08-28T17:32:16Z",
"nvd_published_at" : null
}
}