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CVE-2026-55566 medium CVSS 4.3

Cross-Site Scripting (XSS) in org.yamcs:yamcs-core (CVE-2026-55566)

Summary

Cross-site scripting in org.yamcs:yamcs-core (CVE-2026-55566). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 5.12.8 or later.

Original description

The description as published by the source.

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.

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.

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-55566 has been found in org.yamcs:yamcs-core.
Risk of unauthorized operations or information disclosure. CVSS score: 4.3/10.
What to do: upgrade org.yamcs:yamcs-core to 5.12.8 or later.
If unsure, ask your IT team or search "org.yamcs:yamcs-core CVE-2026-55566" on the vendor's site.

CVE-2026-55566 (org.yamcs:yamcs-core) — CWE-79 / CVSS v3 4.3
Attack vector: remote (network-reachable) / unauthenticated
Patched: 5.12.8 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Cross-site scripting (XSS) (CWE-79) exists in org.yamcs:yamcs-core.

📍 Affected scope

Check the vendor advisory for the affected versions of org.yamcs:yamcs-core.

🔥 Severity

Severity: Medium (CVSS 4.3/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 5.12.8.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで org.yamcs:yamcs-core を使っているサービスとバージョンを洗い出す。

  2. 2
    Apply patch patch 
    Upgrade org.yamcs:yamcs-core to 5.12.8

    ステージング環境で 5.12.8 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

maven org.yamcs:yamcs-core
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.12.8"}]}]

References

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