CVE-2026-33128 | BDVDB-2026-321613 Detail

h3jsh3

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.

Impact#

Per CVSS v3.1: confidentiality impact low, integrity impact high, availability impact none. Attack vector: network.

Weaknesses#

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

References#

Exploit#

No public exploit known

History#

Version 12026-03-20Record published in the CVE List.

Published

Published: 2026-03-20
Last modified: 2026-03-20

Vendor information

Vendor: h3js
Product: h3

All h3js vulnerabilities

Score

7.5 High

EPSS

less than 1%, Very Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 48.8.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Not classified

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

Vulnerable
>= 2.0.0, < 2.0.1-rc.15
Fixed
Not stated
Vulnerable
< 1.15.6
Fixed
Not stated

Scoring System

CVSS v4.0

Not available

CVSS v3.1

7.5 High

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

Metric breakdown
Attack Vector	Network
Attack Complexity	High
Privileges Required	None
User Interaction	None
Scope	Changed
Confidentiality	Low
Integrity	High
Availability	None

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).