CVE-2026-33128
HIGHh3 has a Server-Sent Events Injection via Unsanitized Newlines in Event Stream Fields
Title source: cnaDescription
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.
Scores
CVSS v3
7.5
EPSS
0.0002
EPSS Percentile
5.9%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N
CISA SSVC
Vulnrichment
Exploitation
poc
Automatable
no
Technical Impact
partial
Details
CWE
CWE-93
Status
published
Products (6)
h3/h3
2.0.0
h3/h3
2.0.1 rc10 (13 CPE variants)
h3/h3
< 1.15.6
h3js/h3
< 1.15.6
h3js/h3
>= 2.0.0, < 2.0.1-rc.15
npm/h3
2.0.0 - 2.0.1-rc.15npm
Published
Mar 20, 2026
Tracked Since
Mar 20, 2026