User-context script execution via unvalidated extension name
Published Aug 28, 2026 · Updated Aug 28, 2026
DOM-based XSS in Yamcs before 5.12.8 and 5.13.0 through 5.13.1 allows remote attackers to run JavaScript through a crafted /ext URL. ExtensionComponent.loadExtension interpolates the URL-derived extension name into holder.innerHTML without validation, creating an attacker-selected element. A victim must open the link; the script runs in the Yamcs origin and can read application data available to that user.
Summary
What happened
DOM-based XSS in Yamcs before 5.12.8 and 5.13.0 through 5.13.1 allows remote attackers to run JavaScript through a crafted /ext URL. ExtensionComponent.loadExtension interpolates the URL-derived extension name into holder.innerHTML without validation, creating an attacker-selected element. A victim must open the link; the script runs in the Yamcs origin and can read application data available to that user.
The record
- CVE
- CVE-2026-55566
- Published
- Aug 28, 2026
- Updated
- Aug 28, 2026
- Vendor
- Space Applications Services
- Product
- Yamcs
- Classifications
- CWE-79, T1204.001
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 28, 2026CVE publishedPublication date reported by the CVE source.
- Aug 28, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 5.12.8
- Affected versionversion=>= 5.13.0, < 5.13.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Upstream crafted /ext URL reproductionproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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