CVE-2026-35515
Medium
Description
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.
SeverityMedium
CVSS6.1
Exploit probability—
Product
Nest
PublishedApr 7, 2026
First seenApr 7, 2026
Weakness typeCWE-74Injection
How to fix
Update
- nestjs nest11.1.18 or later
- @nestjs/core11.1.18 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| nestjs nest | v < 11.1.18 | 11.1.18 |
| @nestjs/corenpm | v < 11.1.18 | 11.1.18 |
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