Vulnerability · Published Aug 28, 2026 · Assigned by GitHub_M
CVE-2026-55549Yamcs: Reflected XSS in the URL of the Authorize Endpoint
Medium 6.5
In plain English
A medium-severity cross-site scripting in yamcs from yamcs. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 1.3% (higher than 71% of all known vulnerabilities). Ready-made attack tooling exists: Nuclei. Fixed versions are available - upgrade the affected package.
Official description
Yamcs is a mission control framework. Prior to 5.9.4, Yamcs reflects an attacker-controlled redirect_uri parameter from GET /auth/authorize into yamcs-core/src/main/resources/auth/templates/authorize.html without adequate HTML escaping by yamcs-core/src/main/java/org/yamcs/http/auth/AuthHandler.java and yamcs-core/src/main/java/org/yamcs/http/HandlerContext.java. A crafted authorization URL can execute JavaScript when opened by a Yamcs user. The script can access browser-held authentication material and transmit it to an attacker, enabling account compromise. This issue is fixed in version 5.9.4.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Maven | org.yamcs:yamcs-core | 5.9.4 | GHSA-rxpg-wjf8-qv9c |
Affected products (as reported)
Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
References
- https://github.com/yamcs/yamcs/security/advisories/GHSA-rxpg-wjf8-qv9c x_refsource_CONFIRM
- https://github.com/yamcs/yamcs/commit/4d47d5cdcf5d92c2c5bbbc19feada422923332e3 x_refsource_MISC
- https://github.com/yamcs/yamcs/releases/tag/yamcs-5.9.4 x_refsource_MISC