Junglewise Threat Intelligence

CVE-2026-1528: Node.js undici denial of service via WebSocket length overflow

CVE-2026-1528 · Severity: high · CVSS 7.5 · Published 2026-03-12

Executive brief

Undici is a popular HTTP and WebSocket client for Node.js used to fetch data and maintain real-time connections. A vulnerability in its WebSocket implementation allows a malicious server to crash the client application by sending a specially crafted message with an extremely large length value. This results in a denial-of-service (DoS) condition, potentially disrupting services that rely on Undici for external communications.

Technical details

A vulnerability exists in the Undici WebSocket client's ByteParser component. When a server responds with a WebSocket frame using the 64-bit length form containing an extremely large value, the internal mathematical operations in ByteParser overflow. This causes the parser to enter an invalid state and throw an uncaught TypeError. Because this exception is fatal, it terminates the Node.js process. The issue is classified under CWE-1284 (Improper Validation of Specified Quantity in Input) and CWE-248 (Uncaught Exception). It is fixed in versions 7.24.0 and 6.24.0.

Affected products

  • Node.js undici < 6.24.0, < 7.24.0

Timeline

  • 2026-03-12: disclosed
  • 2026-03-12: advisory
  • 2026-03-12: patched

References