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CVE-2026-25957: Cube.js Crash Course: Async Nightmares and WebSocket Woes

#security #cve #cybersecurity

Cube.js Crash Course: Async Nightmares and WebSocket Woes

Vulnerability ID: CVE-2026-25957
CVSS Score: 6.5
Published: 2026-02-10

Cube.js, the self-proclaimed 'universal semantic layer' for building data applications, suffered from a classic case of Node.js negligence. By failing to properly await asynchronous operations in API handlers and using unsafe data structures for WebSocket subscriptions, the platform exposed a trivial Denial of Service vector. An authenticated attacker can crash the entire server process simply by abruptly closing a connection or confuse the event loop with malformed date strings.

TL;DR

Improper handling of asynchronous errors and lack of input validation in Cube.js allows authenticated attackers to crash the server (DoS) or hang the event loop. Upgrade to version 1.5.13 or 1.4.2 immediately.

⚠️ Exploit Status: POC

Technical Details

  • CWE ID: CWE-755 (Improper Handling of Exceptional Conditions)
  • Attack Vector: Network
  • CVSS Score: 6.5 (Medium)
  • Exploit Status: PoC Available
  • Impact: High Availability Loss
  • Affected Components: API Gateway, LocalSubscriptionStore

Affected Systems

  • Cube.js API Gateway
  • Cube.js Server Core
  • Node.js Runtime (v15+)
  • Cube.js: >= 1.1.17, < 1.4.2 (Fixed in: 1.4.2)
  • Cube.js: >= 1.5.0, < 1.5.13 (Fixed in: 1.5.13)

Code Analysis

Commit: 6271520

Fix unawaited async boundaries in API Gateway

- this.apiGateway.load(req.query)
+ await this.apiGateway.load(req.query)
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Commit: 9e9f9d1

Refactor LocalSubscriptionStore to use Maps

- this.subscriptions = {}
+ this.subscriptions = new Map()
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Exploit Details

  • Internal Research: DoS via unhandled promise rejection in API gateway response handling.

Mitigation Strategies

  • Disable WebSockets if not explicitly required by the application architecture.
  • Implement a reverse proxy (Nginx/HAProxy) with strict timeouts and connection buffering to absorb client disconnects before they hit the Node.js layer.
  • Monitor Node.js process exit codes and UnhandledPromiseRejection logs.

Remediation Steps:

  1. Identify the current Cube.js version using npm list @cubejs-backend/server-core.
  2. Update package.json to require @cubejs-backend/server-core version ^1.5.13 or ^1.4.2.
  3. Rebuild and redeploy the container images.
  4. Verify the fix by monitoring logs for 'UnhandledPromiseRejection' during load testing.

References

Read the full report for CVE-2026-25957 on our website for more details including interactive diagrams and full exploit analysis.

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