CVE-2026-29085: hono Injection

Vulnerability summary

CVE-2026-29085 is a medium (CVSS 6.5) Injection vulnerability in hono. EPSS estimates a 0.30% chance of exploitation in the next 30 days, higher than 21.7% of scored vulnerabilities.

Timeline

1. 04-03-2026
   PublishedVulnerability first disclosed.
2. 05-03-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.