Instituto Nacional de ciberseguridad. Sección Incibe
Instituto Nacional de Ciberseguridad. Sección INCIBE-CERT

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CVE-2026-35515

Severity CVSS v4.0:
MEDIUM
Type:
CWE-74 Injection
Publication date:
07/04/2026
Last modified:
07/04/2026

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.

Impact

Vector 4.0
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:L/SA:N CVSS v4.0 Severity and Metrics:

Base Score: 6.30 MEDIUM
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:L/SA:N

Attack Vector (AV): Network
Attack Complexity (AC): Low
Attack Requirements (AT): Present
Privileges Required (PR): None
User Interaction (UI): None
Confidentiality (VC): None
Integrity (VI): Low
Availability (VA): Low
Confidentiality (SC): None
Integrity (SI): Low
Availability (SA): None

Base Score 4.0
6.30
Severity 4.0
MEDIUM

References to Advisories, Solutions, and Tools