CVE-2026-33128 | THREATINT

Description

H3 is a minimal H(TTP) framework. In versions prior to 1.15.6 and between 2.0.0 through 2.0.1-rc.14, createEventStream is vulnerable to Server-Sent Events (SSE) injection due to missing newline sanitization in formatEventStreamMessage() and formatEventStreamComment(). An attacker who controls any part of an SSE message field (id, event, data, or comment) can inject arbitrary SSE events to connected clients. This issue is fixed in versions 1.15.6 and 2.0.1-rc.15.

PUBLISHED Reserved 2026-03-17 | Published 2026-03-20 | Updated 2026-03-20 | Assigner GitHub_M

HIGH: 7.5CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N

Problem types

CWE-93: Improper Neutralization of CRLF Sequences ('CRLF Injection')

Product status

>= 2.0.0, < 2.0.1-rc.15

affected

< 1.15.6

affected

References

github.com/h3js/h3/security/advisories/GHSA-22cc-p3c6-wpvm

github.com/...ommit/7791538e15ca22437307c06b78fa155bb73632a6

github.com/...b081f044611/src/utils/internal/event-stream.ts

cve.org (CVE-2026-33128)

nvd.nist.gov (CVE-2026-33128)

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