CVE-2026-55549

6.5 MEDIUM 1% exploit odds Fix listed XSS Browser & mail

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in, but needs a user to act. High risk of data exposure.
Exploit odds: 1.3% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-08-28 20:18 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-09-08 21:08 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 1.3% in the next 30 days (EPSS).
Severity: 6.5 MEDIUM (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-08-28 20:18 UTC
Last modified: 2026-09-08 21:08 UTC
Exploit probability: 1.3% · EPSS, next 30 days
Weakness: CWE-79 · Cross-site scripting
Record status: Awaiting Analysis

Attack profile CVSS 3.1 · 6.5

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: Required
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-55549.md and follow it. Check whether this project is affected by CVE-2026-55549. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record