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CVE-2026-77394 high CVSS 7.6

Cross-Site Scripting (XSS) in @openc3/vue-common (CVE-2026-77394)

Summary

Cross-site scripting in @openc3/vue-common (CVE-2026-77394). Confidential information can be exposed externally. Exploitable via POST /openc3-api/screen. Mitigation: upgrade to 7.3.0 or later.

Original description

The description as published by the source.

Summary

A user who can save a telemetry screen (permission system_set) can embed JavaScript in a screen BUTTON widget. The BUTTON widget eval()s the stored button text in the browser when the button is activated, and screens are shared content rendered to other users in the scope. As a result, an attacker's stored JavaScript executes in a different operator's authenticated session — a stored, cross-user XSS (not self-XSS). The payload runs in the COSMOS origin and can read localStorage.openc3Token (the victim's session token), enabling session/account takeover and, via the victim's privileges, a path to server-side code execution through the Script Runner.

The site's Content-Security-Policy permits 'unsafe-inline'/'unsafe-eval' (see "Contributing factor"), so the injected script runs unimpeded.

  • Product: OpenC3 COSMOS (Core; likely Enterprise — see scoping note)
  • Affected version: confirmed 7.2.0 (latest, tested 2026-06-25); the code path is present on main. Lower bound for maintainer to confirm.
  • Reporter: Arpit Kubadia

Description & root cause

  1. Screen save (the store): POST /openc3-api/screen → ScreensController#create (openc3-cosmos-cmd-tlm-api/app/controllers/screens_controller.rb:35-43) persists the raw screen text after authorization('system_set'). No sanitization of the screen body.
  2. The sink (the execution): the BUTTON widget stores the button's action as its second parameter…

Source: NIST National Vulnerability Database 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-2026-77394 has been found in @openc3/vue-common.
Attackers can target a specific entry point like POST /openc3-api/screen over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.6/10.
What to do: upgrade @openc3/vue-common to 7.3.0 or later.
If unsure, ask your IT team or search "@openc3/vue-common CVE-2026-77394" on the vendor's site.

CVE-2026-77394 (@openc3/vue-common) — CWE-79 / CVSS v3 7.6
Attack vector: remote (network-reachable)
Attack surface: POST /openc3-api/screen / system_set / BUTTON / localStorage.openc3Token
Patched: 7.3.0 — 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 @openc3/vue-common. Attackers reach the vulnerable code path via POST /openc3-api/screen.

📍 Affected scope

Check the vendor advisory for the affected versions of @openc3/vue-common. Attack surface: POST /openc3-api/screen / system_set / BUTTON / localStorage.openc3Token.

🔥 Severity

Severity: High (CVSS 7.6/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 7.3.0.

🛡️ 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 POST /openc3-api/screen requests with malformed payloads or SQL meta-characters. Run grep -r '@openc3/vue-common' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

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

  1. 1
    Identify exposure identify 
    grep -r '@openc3/vue-common' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で @openc3/vue-common を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Hunt for indicators of compromise detect 
    grep 'POST /openc3-api/screen' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで POST /openc3-api/screen への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。

  3. 3
    Apply patch patch 
    Upgrade @openc3/vue-common to 7.3.0

    ステージング環境で 7.3.0 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と、Step 2 で見つけた異常検知の続報チェックを含めること。

  4. 4
    Post-deployment verification verify 
    Replay attack against POST /openc3-api/screen on staging to confirm patch closes the vector

    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 Step 2 と同じログクエリでアラート再発が無いか継続監視。

Affected packages

npm @openc3/vue-common
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.3.0"}]}]

References

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