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GHSA-9272-wg2r-7xmx

MediumCVSS 4.3 / 10
Published Aug 28, 2026·Last modified Aug 28, 2026
Affected Components(2)
Maven logoorg.yamcs/yamcs-core
< 5.12.8
Maven logoorg.yamcs/yamcs-core
5.13.0 – 5.13.2
Description

Attack type: Unauthenticated remote Impact: Execution of arbitrary JavaScript in a user’s browser. Affected components: extension.matcher.ts:12, extension.component.ts:40, app.component.ts:134.

Yamcs 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.

<img width="940" height="294" alt="image" src="https://github.com/user-attachments/assets/d886d65c-9bb5-4599-ac11-55db83aafc0e" />

Steps to Reproduce:

  1. Start a Yamcs instance.
  2. Insert the following URL into the browser and press enter (change ‘myproject’ to the name of your instance):
http://localhost:8090/ext/img%20src%3Dx%20onerror%3Dalert%281%29?c=myproject
  1. You will receive an alert with the number ‘1’ in it.

Recommendations:

  1. Use document.createElement instead of innerHTML in extension.component.ts.
  2. Validate the extension against registered plugin IDs.
  3. Enforce a strict custom-element-name regex before mounting.
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Risk Scores
Base Score
4.3

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a low impact on the confidentiality of the information.

Threat Intelligence
4.0

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.38%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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