CVE-2026-35515: Nestjs Nest

Medium severity, CVSS 6.1. EPSS: 0.3% chance of exploitation in the next 30 days.

Nest is a framework for building scalable Node.js server-side applications. Prior to 11.1.18, SseStream._transform() interpolates message.type and message.id directly into Server-Sent Events text protocol output without sanitizing newline characters (\r, \n). Since the SSE protocol treats both \r and \n as field delimiters and \n\n as event boundaries, an attacker who can influence these fields through upstream data sources can inject arbitrary SSE events, spoof event types, and corrupt reconnection state. This vulnerability is fixed in 11.1.18.

Affected products

• Nestjs Nest: before 11.1.18 (fixed in 11.1.18)

Published 2026-04-07. Last modified 2026-06-17.