CVE-2026-55566 Yamcs: DOM XSS in Extension Routing
Attackers can execute arbitrary JavaScript in user browsers via crafted URLs in Yamcs, potentially reading data or performing actions.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-55566?
CVE-2026-55566 is a medium-severity cross-site scripting vulnerability in yamcs, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Yamcs is a mission control framework. Prior to 5.12.8 and 5.13.2, Yamcs processes attacker-controlled data from the /ext URL route in yamcs-web/src/main/webapp/projects/webapp/src/app/core/routes/extension.matcher.ts, extension.component.ts, and app.component.ts without checking registered plugin IDs before DOM rendering through innerHTML. A crafted URL can execute JavaScript when opened by a user. The script can read data available to the Yamcs web application and perform actions in the user context. This issue is fixed in versions 5.12.8 and 5.13.2.
Weakness: CWE-79
Which versions are affected by CVE-2026-55566?
4 open source packages ship an affected version, including org.yamcs:yamcs-core.
| Package | Affected | Fixed in |
|---|---|---|
org.yamcs:yamcs-core Maven | All versions | 5.12.8 |
org.yamcs:yamcs-core Maven | All versions | 5.12.8 |
org.yamcs:yamcs-core Maven | From 5.13.0 | 5.13.2 |
org.yamcs:yamcs-core Maven | From 5.13.0 | 5.13.2 |
How do I fix CVE-2026-55566?
Upgrade org.yamcs:yamcs-core to a fixed version for your release line: 5.12.8 or 5.13.2.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-55566 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55566 exists.
Sources
Also known as GHSA-9272-wg2r-7xmx.