# CVE-2026-55566: Yamcs DOM XSS in Extension Routing

Source: https://junglewise.ai/threats/cve-2026-55566-yamcs-dom-xss-in-extension-routing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-28. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-55566 · Severity: medium · CVSS 4.3 · Published 2026-08-28

Yamcs is a satellite command and telemetry system used for space mission operations. The application contains a cross-site scripting vulnerability in its extension routing system that allows attackers to execute malicious code in users' browsers without authentication. An attacker can craft a phishing link and send it to users; when clicked, it silently executes arbitrary JavaScript, potentially enabling account hijacking, data theft, or further system compromise.

Technologies: [org.yamcs:yamcs-core (Maven)](https://junglewise.ai/threats/technologies/org-yamcs-yamcs-core). Vendors: [Maven](https://junglewise.ai/threats/vendors/maven).

## Quick answers

**Is CVE-2026-55566 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55566 being exploited in the wild.

**How severe is CVE-2026-55566?** Medium severity, with a CVSS score of 4.3, published 28 August 2026.

**Which products and versions are affected?** org.yamcs:yamcs-core (Maven) ECOSYSTEM:introduced=5.13.0,fixed=5.13.2.

**Is there a fix for CVE-2026-55566?** Yes. org.yamcs:yamcs-core (Maven): upgrade to 5.13.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-55566 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-55566?** Check whether you run org.yamcs:yamcs-core (Maven) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- org.yamcs:yamcs-core (Maven): upgrade to 5.13.2 or later

  ```sh
  # set org.yamcs:yamcs-core to 5.13.2 in your pom.xml or build.gradle
  ```


## Technical details

This is a DOM-based XSS vulnerability (CWE-79) in the /ext URL endpoint of Yamcs. The root cause is the unsafe use of innerHTML in extension.component.ts (line 40) combined with insufficient input validation in extension.matcher.ts (line 12) and app.component.ts (line 134). An unauthenticated attacker can inject malicious JavaScript by crafting a URL like http://localhost:8090/ext/img%20src%3Dx%20onerror%3Dalert%281%29?c=myproject. The attack requires user interaction (the user must visit the malicious link). No authentication or special privileges are required. Patches are available in versions 5.12.8 and 5.13.2, which implement fixes such as using document.createElement instead of innerHTML, validating extensions against registered plugin IDs, and enforcing strict custom-element-name regex validation.

## Affected products

- Yamcs Yamcs 5.13.0-5.13.1, 5.12.7 and earlier

## Identifiers

- CVE-2026-55566
- GHSA-9272-wg2r-7xmx

## Timeline

- 2026-07-14: disclosed: Vulnerability published to GitHub Advisory Database
- 2026-08-28: advisory: Advisory updated and reviewed on GitHub
- 2026-08-28: patched: Patches released in versions 5.12.8 and 5.13.2

## References

- [https://api.github.com/users/suffs811](https://api.github.com/users/suffs811)
- [https://github.com/suffs811](https://github.com/suffs811)
- [https://api.github.com/users/suffs811/gists%7B/gist_id%7D](https://api.github.com/users/suffs811/gists%7B/gist_id%7D)
- [https://api.github.com/users/suffs811/repos](https://api.github.com/users/suffs811/repos)
- [https://avatars.githubusercontent.com/u/84633135?v=4](https://avatars.githubusercontent.com/u/84633135?v=4)
- [https://api.github.com/users/suffs811/events%7B/privacy%7D](https://api.github.com/users/suffs811/events%7B/privacy%7D)

## Related threats

- [Yamcs remote code execution via unescaped StreamSQL LIKE pattern](https://junglewise.ai/threats/cve-2026-55565-yamcs-remote-code-execution-via-unescaped-streamsql-like-pattern)
- [Yamcs remote code execution via YAML injection in instance template](https://junglewise.ai/threats/cve-2026-55559-yamcs-remote-code-execution-via-yaml-injection-in-instance)
- [Yamcs unauthenticated directory traversal](https://junglewise.ai/threats/cve-2026-55552-yamcs-unauthenticated-directory-traversal)
- [Yamcs reflected XSS in authorize endpoint](https://junglewise.ai/threats/cve-2026-55549-yamcs-reflected-xss-in-authorize-endpoint)
- [Yamcs missing authorization on role and privilege enumeration endpoints](https://junglewise.ai/threats/cve-2026-55547-yamcs-missing-authorization-on-role-and-privilege-enumeration)