Vulnerability in Marimo remote-attack (CVE-2026-39987, KEV)

Summary

vulnerability in Marimo remote-attack (CVE-2026-39987). Risk of unauthorized operations or information disclosure. Listed in CISA KEV — actively exploited.

Original description

The description as published by the source.

Summary

Marimo (19.6k stars) has a Pre-Auth RCE vulnerability. The terminal WebSocket endpoint /terminal/ws lacks authentication validation, allowing an unauthenticated attacker to obtain a full PTY shell and execute arbitrary system commands.

Unlike other WebSocket endpoints (e.g., /ws) that correctly call validate_auth() for authentication, the /terminal/ws endpoint only checks the running mode and platform support before accepting connections, completely skipping authentication verification.

Affected Versions

Marimo <= 0.20.4

Vulnerability Details

Root Cause: Terminal WebSocket Missing Authentication

marimo/_server/api/endpoints/terminal.py lines 340-356:

@router.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket) -> None:
    app_state = AppState(websocket)
    if app_state.mode != SessionMode.EDIT:
        await websocket.close(...)
        return
    if not supports_terminal():
        await websocket.close(...)
        return
    # No authentication check!
    await websocket.accept()  # Accepts connection directly
    # ...
    child_pid, fd = pty.fork()  # Creates PTY shell

Compare with the correctly implemented /ws endpoint (ws_endpoint.py lines 67-82):

@router.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket) -> None:
    app_state = AppState(websocket)
    validator = WebSocketConnectionValidator(websocket, app_state)
    if not await validator.validate_auth():  # Corr…

Source: CISA Known Exploited Vulnerabilities NVD GitHub Advisory CISA KEV

AI summary

Written by an external AI model and may contain mistakes. Check the original description and references below before acting on it.

There is a serious issue with Marimo's product that might allow attackers to access certain codes and manipulate company's systems. Unless proper security measures are taken, there is a risk of information leakage and business disruption. It's crucial to promptly apply security patches. This case carries risks similar to past incidents like the Heartbleed bug.

CVE-2026-39987 in Marimo products presents a significant RCE vulnerability allowing unauthenticated exploitation. The specific HTTP endpoints or function names are not specified within the given material, but it relates to CWE-306, indicating risks of arbitrary system command execution. Affected version range and fixes also could not be determined from official resources. While the exact workaround is unclear, enhancing overall system access controls and monitoring is advisable. The CVSS interpretation confirms remote exploitation capability and no need for authentication.

❓ What is the problem

Marimo製品におけるRCE脆弱性

📍 Affected scope

具体的な関数名・エンドポイント不明

🔥 Severity

重大（high）

🔧 How to fix

公式パッチ適用

🛡️ Workaround

素材から特定できず

🔍 Detection

素材から特定できず

Related past incidents Similar incidents extracted from past CVEs

Heartbleed

OpenSSLのバグにより、メモリを攻撃者が盗み見ることができた事例。

Log4Shell

Log4jにおいてRCEを可能にした深刻な脆弱性。

If this happens at your company Expected impact per business scenario

📌 ECサイトの場

顧客情報が不正に取得され、金銭被害や信用低下が発生する可能性がある。

📌 社内システムの場

システムダウンにより業務が停止し、生産性やビジネスに大きな影響が出る可能性がある。

📌 クラウドサービス事業者の場

顧客のデータリークが発生し、契約解消や損害賠償問題に発展する可能性がある。

Recommended action

即時のパッチ適用とセキュリティ監視の強化を推奨する。

Response actions

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

1
Identify exposure identify
```
grep -r 'remote-attack' . | 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 remote-attack を grep し、稼働しているサービス・バージョンを把握する。
4
Consider incident declaration escalate
```
Notify SOC / on-call
```
CISA KEV登録済 = 実環境で悪用が観測されている。Step 3 で兆候があればインシデント対応宣言、無くてもパッチ適用までWAF強化を最優先で。
7
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 Step 3 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

PyPI marimo

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.23.0"}]}]

References

advisory NVD
advisory github.com
package github.com
package pypi.org
web github.com
web github.com
web github.com
web cisa.gov
web cisa.gov
web sysdig.com