CVE-2026-29085 MEDIUM

CVE-2026-29085: Hono: SSE Control Field Injection via CR/LF in writeSSE()

Vendor Honojs
Product hono
Weakness CWE-74
Published March 4, 2026
Last update March 5, 2026

CVSS base score

6.5/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality Low
Integrity Low

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

What the vulnerability does

01Description

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to version 4.12.4, when using streamSSE() in Streaming Helper, the event, id, and retry fields were not validated for carriage return (\r) or newline (\n) characters. Because the SSE protocol uses line breaks as field delimiters, this could allow injection of additional SSE fields within the same event frame if untrusted input was passed into these fields. This issue has been patched in version 4.12.4.

Key dates

02Disclosure timeline

March 4, 2026 CVE published
March 5, 2026 Record updated